最近看了一發mybatis 源碼 簡單做個記錄 如有做的不好的 見諒
MyBatis 是一款優秀的持久層架構，它支援定制化 SQL、存儲過程以及進階映射。MyBatis 避免了幾乎所有的 JDBC 代碼和手動設定參數以及擷取結果集。MyBatis 可以使用簡單的 XML 或注解來配置和映射原生類型、接口和 Java 的 POJO（Plain Old Java Objects，普通老式 Java 對象）為資料庫中的記錄。
詳細内容可以 mybatis 文檔
首先完成基本操作 然後通過test進行 檢視源碼
1.首先建立表
CREATE TABLE `blog` (
`bid` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(255) DEFAULT NULL
PRIMARY KEY (`bid`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;
INSERT INTO `blog` (`bid`, `name`) VALUES (1, 'mq學習');
INSERT INTO `blog` (`bid`, `name`) VALUES (2, 'redis安裝入門');
2,建立model 建立mapper
@Data
public class Blog implements Serializable{
private Integer bid; // 文章ID
private String name; // 文章标題
}
public interface BlogMapper {
/**
* 根據主鍵查詢文章
* @param bid
* @return
*/
Blog selectBlogById(@param("bid")Integer bid);
}
然後建立mapper.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapper接口路徑">
<resultMap id="BaseResultMap" type="model類路徑">
<id column="bid" property="bid" jdbcType="INTEGER"/>
<id column="name" property="name" jdbcType="VARCHAR"/>
</resultMap>
<select id="selectBlogById" resultMap="BaseResultMap" >
select * from blog where bid = #{bid}
</select>
</mapper>
基礎操作類完成
建立mybatis 配置檔案
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<properties resource="db.properties"></properties>
<settings>
<!-- 列印查詢語句 -->
<setting name="logImpl" value="STDOUT_LOGGING" />
<!-- 控制全局緩存（二級緩存）-->
<setting name="cacheEnabled" value="true"/>
<!-- 延遲加載的全局開關。當開啟時，所有關聯對象都會延遲加載。預設 false -->
<setting name="lazyLoadingEnabled" value="true"/>
<!-- 當開啟時，任何方法的調用都會加載該對象的所有屬性。預設 false，可通過select标簽的 fetchType來覆寫-->
<setting name="aggressiveLazyLoading" value="false"/>
<!-- Mybatis 建立具有延遲加載能力的對象所用到的代理工具，預設JAVASSIST -->
<!--<setting name="proxyFactory" value="JAVASSIST" />-->
<setting name="localCacheScope" value="SESSION"/>
</settings>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/><!-- 單獨使用時配置成MANAGED沒有事務 -->
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driver}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="BlogMapper.xml" />
</mappers>
</configuration>
資源引用了 db.properties
建立檔案db.properties 放到resource目錄下
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8&rewriteBatchedStatements=true
#資料庫賬号
jdbc.username=xxxx
#資料庫密碼
jdbc.password=xxxx
路徑如圖
pom依賴
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.1</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.21</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>RELEASE</version>
</dependency>
<!-- lombok -->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.16.6</version>
</dependency>
建立test類
public class MyBatisTest {
/**
* 使用MyBatis API方式
* @throws IOException
*/
@Test
public void testStatement() throws IOException {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession session = sqlSessionFactory.openSession();
try {
Blog blog = (Blog) session.selectOne("com.gupaoedu.mapper.BlogMapper.selectBlogById", 1);
System.out.println(blog);
} finally {
session.close();
}
}
/**
* 通過 SqlSession.getMapper(XXXMapper.class) 接口方式
* @throws IOException
*/
@Test
public void testSelect() throws IOException {
String resource = "mybatis-config.xml";
//将mybatis配置檔案讀取成流
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// ExecutorType.BATCH 執行器 類型
SqlSession session = sqlSessionFactory.openSession();
try {
BlogMapper mapper = session.getMapper(BlogMapper.class);
Blog blog = mapper.selectBlogById(1);
System.out.println(blog);
} finally {
session.close();
}
}
}
//接下來進入源碼分析環節
SqlSessionFactoryBuilder SqlSessionFactory建造器
public SqlSessionFactory build(InputStream inputStream) {
return this.build((InputStream)inputStream, (String)null, (Properties)null);
}
public SqlSessionFactory build(InputStream inputStream,
String environment, Properties properties) {
try {
//初始化一個 XMLConfigBuilder
XMLConfigBuilder parser = new XMLConfigBuilder(inputStream, environment, properties);
return build(parser.parse());
} catch (Exception e) {
throw ExceptionFactory.wrapException("Error building SqlSession.", e);
} finally {
ErrorContext.instance().reset();
try {
inputStream.close();
} catch (IOException e) {
// Intentionally ignore. Prefer previous error.
}
}
}
//XMLConfigBuilder 構造
public XMLConfigBuilder(InputStream inputStream, String environment, Properties props) {
this(new XPathParser(inputStream, true, props,
new XMLMapperEntityResolver()), environment, props);
}
//XMLMapperEntityResolver Offline entity resolver for the MyBatis DTDs. mybatis DTDs 解析
//XPathParser 構造
public XPathParser(InputStream inputStream, boolean validation, Properties variables, EntityResolver entityResolver) {
commonConstructor(validation, variables, entityResolver);
//根據流建立文檔對象
this.document = createDocument(new InputSource(inputStream));
}
//公共構造
private void commonConstructor(boolean validation, Properties variables, EntityResolver entityResolver) {
this.validation = validation;
this.entityResolver = entityResolver;
this.variables = variables;
XPathFactory factory = XPathFactory.newInstance();
this.xpath = factory.newXPath();
}
//建立文檔對象
private Document createDocument(InputSource inputSource) {
// important: this must only be called AFTER common constructor
try {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setValidating(validation);
factory.setNamespaceAware(false);
factory.setIgnoringComments(true);
factory.setIgnoringElementContentWhitespace(false);
factory.setCoalescing(false);
factory.setExpandEntityReferences(true);
DocumentBuilder builder = factory.newDocumentBuilder();
builder.setEntityResolver(entityResolver);
builder.setErrorHandler(new ErrorHandler() {
@Override
public void error(SAXParseException exception) throws SAXException {
throw exception;
}
@Override
public void fatalError(SAXParseException exception) throws SAXException {
throw exception;
}
@Override
public void warning(SAXParseException exception) throws SAXException {
}
});
return builder.parse(inputSource);
} catch (Exception e) {
throw new BuilderException("Error creating document instance. Cause: " + e, e);
}
}
//XMLConfigBuilder 再次調用
private XMLConfigBuilder(XPathParser parser, String environment, Properties props) {
super(new Configuration());
ErrorContext.instance().resource("SQL Mapper Configuration");
this.configuration.setVariables(props);
this.parsed = false;
this.environment = environment;
this.parser = parser;
}
//XMLConfigBuilder 的parse 解析方法
public Configuration parse() {
if (parsed) {
throw new BuilderException("Each XMLConfigBuilder can only be used once.");
}
parsed = true;
//解析配置
parseConfiguration(parser.evalNode("/configuration"));
return configuration;
}
public XNode evalNode(String expression) {
return evalNode(document, expression);
}
public XNode evalNode(Object root, String expression) {
Node node = (Node) evaluate(expression, root, XPathConstants.NODE);
if (node == null) {
return null;
}
return new XNode(this, node, variables);
}
private Object evaluate(String expression, Object root, QName returnType) {
try {
//具體實作
return xpath.evaluate(expression, root, returnType);
} catch (Exception e) {
throw new BuilderException("Error evaluating XPath. Cause: " + e, e);
}
}
public Object evaluate(String expression, Object item, QName returnType)
throws XPathExpressionException {
if ( expression == null ) {
String fmsg = XSLMessages.createXPATHMessage(
XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
new Object[] {"XPath expression"} );
throw new NullPointerException ( fmsg );
}
if ( returnType == null ) {
String fmsg = XSLMessages.createXPATHMessage(
XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
new Object[] {"returnType"} );
throw new NullPointerException ( fmsg );
}
// Checking if requested returnType is supported. returnType need to
// be defined in XPathConstants
if ( !isSupported ( returnType ) ) {
String fmsg = XSLMessages.createXPATHMessage(
XPATHErrorResources.ER_UNSUPPORTED_RETURN_TYPE,
new Object[] { returnType.toString() } );
throw new IllegalArgumentException ( fmsg );
}
try {
XObject resultObject = eval( expression, item );
return getResultAsType( resultObject, returnType );
} catch ( java.lang.NullPointerException npe ) {
// If VariableResolver returns null Or if we get
// NullPointerException at this stage for some other reason
// then we have to reurn XPathException
throw new XPathExpressionException ( npe );
} catch ( javax.xml.transform.TransformerException te ) {
Throwable nestedException = te.getException();
if ( nestedException instanceof javax.xml.xpath.XPathFunctionException ) {
throw (javax.xml.xpath.XPathFunctionException)nestedException;
} else {
// For any other exceptions we need to throw
// XPathExpressionException ( as per spec )
throw new XPathExpressionException ( te );
}
}
}
private void parseConfiguration(XNode root) {
try {
//issue #117 read properties first
//properties 元素
propertiesElement(root.evalNode("properties"));
Properties settings = settingsAsProperties(root.evalNode("settings"));
//擷取 Vitual File System 的自定義實作類
loadCustomVfs(settings);
//加載自定義log實作
loadCustomLogImpl(settings);
//别名元素解析
typeAliasesElement(root.evalNode("typeAliases"));
//插件元素 解析
pluginElement(root.evalNode("plugins"));
//對象工廠解析
objectFactoryElement(root.evalNode("objectFactory"));
objectWrapperFactoryElement(root.evalNode("objectWrapperFactory"));
reflectorFactoryElement(root.evalNode("reflectorFactory"));
//設定屬性
settingsElement(settings);
// read it after objectFactory and objectWrapperFactory issue #631
environmentsElement(root.evalNode("environments"));
databaseIdProviderElement(root.evalNode("databaseIdProvider"));
typeHandlerElement(root.evalNode("typeHandlers"));
mapperElement(root.evalNode("mappers"));
} catch (Exception e) {
throw new BuilderException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
}
}
private void settingsElement(Properties props) {
configuration.setAutoMappingBehavior(AutoMappingBehavior.valueOf(props.getProperty("autoMappingBehavior", "PARTIAL")));
configuration.setAutoMappingUnknownColumnBehavior(AutoMappingUnknownColumnBehavior.valueOf(props.getProperty("autoMappingUnknownColumnBehavior", "NONE")));
configuration.setCacheEnabled(booleanValueOf(props.getProperty("cacheEnabled"), true));
configuration.setProxyFactory((ProxyFactory) createInstance(props.getProperty("proxyFactory")));
configuration.setLazyLoadingEnabled(booleanValueOf(props.getProperty("lazyLoadingEnabled"), false));
configuration.setAggressiveLazyLoading(booleanValueOf(props.getProperty("aggressiveLazyLoading"), false));
configuration.setMultipleResultSetsEnabled(booleanValueOf(props.getProperty("multipleResultSetsEnabled"), true));
configuration.setUseColumnLabel(booleanValueOf(props.getProperty("useColumnLabel"), true));
configuration.setUseGeneratedKeys(booleanValueOf(props.getProperty("useGeneratedKeys"), false));
configuration.setDefaultExecutorType(ExecutorType.valueOf(props.getProperty("defaultExecutorType", "SIMPLE")));
configuration.setDefaultStatementTimeout(integerValueOf(props.getProperty("defaultStatementTimeout"), null));
configuration.setDefaultFetchSize(integerValueOf(props.getProperty("defaultFetchSize"), null));
configuration.setMapUnderscoreToCamelCase(booleanValueOf(props.getProperty("mapUnderscoreToCamelCase"), false));
configuration.setSafeRowBoundsEnabled(booleanValueOf(props.getProperty("safeRowBoundsEnabled"), false));
configuration.setLocalCacheScope(LocalCacheScope.valueOf(props.getProperty("localCacheScope", "SESSION")));
configuration.setJdbcTypeForNull(JdbcType.valueOf(props.getProperty("jdbcTypeForNull", "OTHER")));
//設定延遲加載觸發方法
configuration.setLazyLoadTriggerMethods(stringSetValueOf(props.getProperty("lazyLoadTriggerMethods"), "equals,clone,hashCode,toString"));
configuration.setSafeResultHandlerEnabled(booleanValueOf(props.getProperty("safeResultHandlerEnabled"), true));
configuration.setDefaultScriptingLanguage(resolveClass(props.getProperty("defaultScriptingLanguage")));
configuration.setDefaultEnumTypeHandler(resolveClass(props.getProperty("defaultEnumTypeHandler")));
configuration.setCallSettersOnNulls(booleanValueOf(props.getProperty("callSettersOnNulls"), false));
configuration.setUseActualParamName(booleanValueOf(props.getProperty("useActualParamName"), true));
configuration.setReturnInstanceForEmptyRow(booleanValueOf(props.getProperty("returnInstanceForEmptyRow"), false));
configuration.setLogPrefix(props.getProperty("logPrefix"));
configuration.setConfigurationFactory(resolveClass(props.getProperty("configurationFactory")));
}
//mapper元素
private void mapperElement(XNode parent) throws Exception {
if (parent != null) {
for (XNode child : parent.getChildren()) {
if ("package".equals(child.getName())) {
String mapperPackage = child.getStringAttribute("name");
configuration.addMappers(mapperPackage);
} else {
String resource = child.getStringAttribute("resource");
String url = child.getStringAttribute("url");
String mapperClass = child.getStringAttribute("class");
if (resource != null && url == null && mapperClass == null) {
ErrorContext.instance().resource(resource);
InputStream inputStream = Resources.getResourceAsStream(resource);
//解析 xml
XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, resource, configuration.getSqlFragments());
mapperParser.parse();
} else if (resource == null && url != null && mapperClass == null) {
ErrorContext.instance().resource(url);
InputStream inputStream = Resources.getUrlAsStream(url);
//解析 xml
XMLMapperBuilder mapperParser = new XMLMapperBuilder(inputStream, configuration, url, configuration.getSqlFragments());
mapperParser.parse();
} else if (resource == null && url == null && mapperClass != null) {
Class<?> mapperInterface = Resources.classForName(mapperClass);
//添加mapper
configuration.addMapper(mapperInterface);
} else {
throw new BuilderException("A mapper element may only specify a url, resource or class, but not more than one.");
}
}
}
}
}
//XMLMapperBuilder parse
public void parse() {
if (!configuration.isResourceLoaded(resource)) {
//mapper 資源沒有被加載
//配置元素
configurationElement(parser.evalNode("/mapper"));
configuration.addLoadedResource(resource);
//綁定 mapper 命名空間
bindMapperForNamespace();
}
parsePendingResultMaps();
parsePendingCacheRefs();
parsePendingStatements();
}
private void configurationElement(XNode context) {
try {
String namespace = context.getStringAttribute("namespace");
if (namespace == null || namespace.equals("")) {
throw new BuilderException("Mapper's namespace cannot be empty");
}
builderAssistant.setCurrentNamespace(namespace);
cacheRefElement(context.evalNode("cache-ref"));
cacheElement(context.evalNode("cache"));
parameterMapElement(context.evalNodes("/mapper/parameterMap"));
resultMapElements(context.evalNodes("/mapper/resultMap"));
sqlElement(context.evalNodes("/mapper/sql"));
buildStatementFromContext(context.evalNodes("select|insert|update|delete"));
} catch (Exception e) {
throw new BuilderException("Error parsing Mapper XML. The XML location is '" + resource + "'. Cause: " + e, e);
}
}
private void bindMapperForNamespace() {
String namespace = builderAssistant.getCurrentNamespace();
if (namespace != null) {
Class<?> boundType = null;
try {
boundType = Resources.classForName(namespace);
} catch (ClassNotFoundException e) {
//ignore, bound type is not required
}
if (boundType != null) {
if (!configuration.hasMapper(boundType)) {
// Spring may not know the real resource name so we set a flag
// to prevent loading again this resource from the mapper interface
// look at MapperAnnotationBuilder#loadXmlResource
configuration.addLoadedResource("namespace:" + namespace);
configuration.addMapper(boundType);
}
}
}
}
private void parsePendingResultMaps() {
Collection<ResultMapResolver> incompleteResultMaps = configuration.getIncompleteResultMaps();
synchronized (incompleteResultMaps) {
Iterator<ResultMapResolver> iter = incompleteResultMaps.iterator();
while (iter.hasNext()) {
try {
iter.next().resolve();
iter.remove();
} catch (IncompleteElementException e) {
// ResultMap is still missing a resource...
}
}
}
}
//添加到結果 ResultMap
public ResultMap resolve() {
return assistant.addResultMap(this.id, this.type,this.extend,
this.discriminator, this.resultMappings,this.autoMapping);
}
private void parsePendingCacheRefs() {
Collection<CacheRefResolver> incompleteCacheRefs = configuration.getIncompleteCacheRefs();
synchronized (incompleteCacheRefs) {
Iterator<CacheRefResolver> iter = incompleteCacheRefs.iterator();
while (iter.hasNext()) {
try {
iter.next().resolveCacheRef();
iter.remove();
} catch (IncompleteElementException e) {
// Cache ref is still missing a resource...
}
}
}
}
public Cache resolveCacheRef() {
return assistant.useCacheRef(cacheRefNamespace);
}
private void parsePendingStatements() {
Collection<XMLStatementBuilder> incompleteStatements = configuration.getIncompleteStatements();
synchronized (incompleteStatements) {
Iterator<XMLStatementBuilder> iter = incompleteStatements.iterator();
while (iter.hasNext()) {
try {
iter.next().parseStatementNode();
iter.remove();
} catch (IncompleteElementException e) {
// Statement is still missing a resource...
}
}
}
}
//解析 statement 節點
public void parseStatementNode() {
String id = context.getStringAttribute("id");
String databaseId = context.getStringAttribute("databaseId");
if (!databaseIdMatchesCurrent(id, databaseId, this.requiredDatabaseId)) {
return;
}
Integer fetchSize = context.getIntAttribute("fetchSize");
Integer timeout = context.getIntAttribute("timeout");
String parameterMap = context.getStringAttribute("parameterMap");
String parameterType = context.getStringAttribute("parameterType");
Class<?> parameterTypeClass = resolveClass(parameterType);
String resultMap = context.getStringAttribute("resultMap");
String resultType = context.getStringAttribute("resultType");
String lang = context.getStringAttribute("lang");
LanguageDriver langDriver = getLanguageDriver(lang);
Class<?> resultTypeClass = resolveClass(resultType);
String resultSetType = context.getStringAttribute("resultSetType");
StatementType statementType = StatementType.valueOf(context.getStringAttribute("statementType", StatementType.PREPARED.toString()));
ResultSetType resultSetTypeEnum = resolveResultSetType(resultSetType);
String nodeName = context.getNode().getNodeName();
SqlCommandType sqlCommandType = SqlCommandType.valueOf(nodeName.toUpperCase(Locale.ENGLISH));
boolean isSelect = sqlCommandType == SqlCommandType.SELECT;
boolean flushCache = context.getBooleanAttribute("flushCache", !isSelect);
boolean useCache = context.getBooleanAttribute("useCache", isSelect);
boolean resultOrdered = context.getBooleanAttribute("resultOrdered", false);
// Include Fragments before parsing
XMLIncludeTransformer includeParser = new XMLIncludeTransformer(configuration, builderAssistant);
includeParser.applyIncludes(context.getNode());
// Parse selectKey after includes and remove them.
processSelectKeyNodes(id, parameterTypeClass, langDriver);
// Parse the SQL (pre: <selectKey> and <include> were parsed and removed)
SqlSource sqlSource = langDriver.createSqlSource(configuration, context, parameterTypeClass);
String resultSets = context.getStringAttribute("resultSets");
String keyProperty = context.getStringAttribute("keyProperty");
String keyColumn = context.getStringAttribute("keyColumn");
KeyGenerator keyGenerator;
String keyStatementId = id + SelectKeyGenerator.SELECT_KEY_SUFFIX;
keyStatementId = builderAssistant.applyCurrentNamespace(keyStatementId, true);
if (configuration.hasKeyGenerator(keyStatementId)) {
keyGenerator = configuration.getKeyGenerator(keyStatementId);
} else {
keyGenerator = context.getBooleanAttribute("useGeneratedKeys",
configuration.isUseGeneratedKeys() && SqlCommandType.INSERT.equals(sqlCommandType))
? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE;
}
//添加 mapper statement
builderAssistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType,
fetchSize, timeout, parameterMap, parameterTypeClass, resultMap, resultTypeClass,
resultSetTypeEnum, flushCache, useCache, resultOrdered,
keyGenerator, keyProperty, keyColumn, databaseId, langDriver, resultSets);
}
public MappedStatement addMappedStatement(
String id,
SqlSource sqlSource,
StatementType statementType,
SqlCommandType sqlCommandType,
Integer fetchSize,
Integer timeout,
String parameterMap,
Class<?> parameterType,
String resultMap,
Class<?> resultType,
ResultSetType resultSetType,
boolean flushCache,
boolean useCache,
boolean resultOrdered,
KeyGenerator keyGenerator,
String keyProperty,
String keyColumn,
String databaseId,
LanguageDriver lang,
String resultSets) {
if (unresolvedCacheRef) {
throw new IncompleteElementException("Cache-ref not yet resolved");
}
id = applyCurrentNamespace(id, false);
boolean isSelect = sqlCommandType == SqlCommandType.SELECT;
MappedStatement.Builder statementBuilder = new MappedStatement.Builder(configuration, id, sqlSource, sqlCommandType)
.resource(resource)
.fetchSize(fetchSize)
.timeout(timeout)
.statementType(statementType)
.keyGenerator(keyGenerator)
.keyProperty(keyProperty)
.keyColumn(keyColumn)
.databaseId(databaseId)
.lang(lang)
.resultOrdered(resultOrdered)
.resultSets(resultSets)
.resultMaps(getStatementResultMaps(resultMap, resultType, id))
.resultSetType(resultSetType)
.flushCacheRequired(valueOrDefault(flushCache, !isSelect))
.useCache(valueOrDefault(useCache, isSelect))
.cache(currentCache);
ParameterMap statementParameterMap = getStatementParameterMap(parameterMap, parameterType, id);
if (statementParameterMap != null) {
statementBuilder.parameterMap(statementParameterMap);
}
MappedStatement statement = statementBuilder.build();
configuration.addMappedStatement(statement);
return statement;
}
//XMLMapperBuilder 解析完成 通過 configuration.addMapper(mapperInterface);
//添加mapper
public <T> void addMapper(Class<T> type) {
mapperRegistry.addMapper(type);
}
private final Map<Class<?>, MapperProxyFactory<?>> knownMappers
= new HashMap<Class<?>, MapperProxyFactory<?>>();
//MapperRegistry類
public <T> void addMapper(Class<T> type) {
if (type.isInterface()) {
if (hasMapper(type)) {
throw new BindingException("Type " + type + " is already known to the MapperRegistry.");
}
boolean loadCompleted = false;
try {
knownMappers.put(type, new MapperProxyFactory<T>(type));
// It's important that the type is added before the parser is run
// otherwise the binding may automatically be attempted by the
// mapper parser. If the type is already known, it won't try.
//mapper 注解解析
MapperAnnotationBuilder parser = new MapperAnnotationBuilder(config, type);
parser.parse();
loadCompleted = true;
} finally {
if (!loadCompleted) {
//未加載完成 進行 移除
knownMappers.remove(type);
}
}
}
}
//MapperAnnotationBuilder 解析 注解 解析
public void parse() {
String resource = type.toString();
if (!configuration.isResourceLoaded(resource)) {
//資源沒有被加載 進行加載資源
loadXmlResource();
configuration.addLoadedResource(resource);
//設定目前命名空間
assistant.setCurrentNamespace(type.getName());
parseCache();
parseCacheRef();
Method[] methods = type.getMethods();
for (Method method : methods) {
try {
// issue #237
if (!method.isBridge()) {
parseStatement(method);
}
} catch (IncompleteElementException e) {
configuration.addIncompleteMethod(new MethodResolver(this, method));
}
}
}
parsePendingMethods();
}
//解析緩存
private void parseCache() {
CacheNamespace cacheDomain = type.getAnnotation(CacheNamespace.class);
if (cacheDomain != null) {
Integer size = cacheDomain.size() == 0 ? null : cacheDomain.size();
Long flushInterval = cacheDomain.flushInterval() == 0 ? null : cacheDomain.flushInterval();
Properties props = convertToProperties(cacheDomain.properties());
assistant.useNewCache(cacheDomain.implementation(), cacheDomain.eviction(), flushInterval, size, cacheDomain.readWrite(), cacheDomain.blocking(), props);
}
}
//緩存引用
private void parseCacheRef() {
CacheNamespaceRef cacheDomainRef = type.getAnnotation(CacheNamespaceRef.class);
if (cacheDomainRef != null) {
Class<?> refType = cacheDomainRef.value();
String refName = cacheDomainRef.name();
if (refType == void.class && refName.isEmpty()) {
throw new BuilderException("Should be specified either value() or name() attribute in the @CacheNamespaceRef");
}
if (refType != void.class && !refName.isEmpty()) {
throw new BuilderException("Cannot use both value() and name() attribute in the @CacheNamespaceRef");
}
String namespace = (refType != void.class) ? refType.getName() : refName;
assistant.useCacheRef(namespace);
}
}
//解析語句
void parseStatement(Method method) {
//擷取方法參數類型
Class<?> parameterTypeClass = getParameterType(method);
LanguageDriver languageDriver = getLanguageDriver(method);
SqlSource sqlSource = getSqlSourceFromAnnotations(method, parameterTypeClass, languageDriver);
if (sqlSource != null) {
Options options = method.getAnnotation(Options.class);
final String mappedStatementId = type.getName() + "." + method.getName();
Integer fetchSize = null;
Integer timeout = null;
StatementType statementType = StatementType.PREPARED;
ResultSetType resultSetType = ResultSetType.FORWARD_ONLY;
SqlCommandType sqlCommandType = getSqlCommandType(method);
boolean isSelect = sqlCommandType == SqlCommandType.SELECT;
boolean flushCache = !isSelect;
boolean useCache = isSelect;
KeyGenerator keyGenerator;
String keyProperty = "id";
String keyColumn = null;
if (SqlCommandType.INSERT.equals(sqlCommandType) || SqlCommandType.UPDATE.equals(sqlCommandType)) {
// first check for SelectKey annotation - that overrides everything else
SelectKey selectKey = method.getAnnotation(SelectKey.class);
if (selectKey != null) {
keyGenerator = handleSelectKeyAnnotation(selectKey, mappedStatementId, getParameterType(method), languageDriver);
keyProperty = selectKey.keyProperty();
} else if (options == null) {
keyGenerator = configuration.isUseGeneratedKeys() ? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE;
} else {
keyGenerator = options.useGeneratedKeys() ? Jdbc3KeyGenerator.INSTANCE : NoKeyGenerator.INSTANCE;
keyProperty = options.keyProperty();
keyColumn = options.keyColumn();
}
} else {
keyGenerator = NoKeyGenerator.INSTANCE;
}
if (options != null) {
if (FlushCachePolicy.TRUE.equals(options.flushCache())) {
flushCache = true;
} else if (FlushCachePolicy.FALSE.equals(options.flushCache())) {
flushCache = false;
}
useCache = options.useCache();
fetchSize = options.fetchSize() > -1 || options.fetchSize() == Integer.MIN_VALUE ? options.fetchSize() : null; //issue #348
timeout = options.timeout() > -1 ? options.timeout() : null;
statementType = options.statementType();
resultSetType = options.resultSetType();
}
String resultMapId = null;
ResultMap resultMapAnnotation = method.getAnnotation(ResultMap.class);
if (resultMapAnnotation != null) {
String[] resultMaps = resultMapAnnotation.value();
StringBuilder sb = new StringBuilder();
for (String resultMap : resultMaps) {
if (sb.length() > 0) {
sb.append(",");
}
sb.append(resultMap);
}
resultMapId = sb.toString();
} else if (isSelect) {
resultMapId = parseResultMap(method);
}
assistant.addMappedStatement(
mappedStatementId,
sqlSource,
statementType,
sqlCommandType,
fetchSize,
timeout,
// ParameterMapID
null,
parameterTypeClass,
resultMapId,
getReturnType(method),
resultSetType,
flushCache,
useCache,
// TODO gcode issue #577
false,
keyGenerator,
keyProperty,
keyColumn,
// DatabaseID
null,
languageDriver,
// ResultSets
options != null ? nullOrEmpty(options.resultSets()) : null);
}
}
private void parsePendingMethods() {
Collection<MethodResolver> incompleteMethods = configuration.getIncompleteMethods();
synchronized (incompleteMethods) {
Iterator<MethodResolver> iter = incompleteMethods.iterator();
while (iter.hasNext()) {
try {
iter.next().resolve();
iter.remove();
} catch (IncompleteElementException e) {
// This method is still missing a resource
}
}
}
}
//最終實作方法 通過XMLConfigBuilder 的parse方法 解析了 configration
public SqlSessionFactory build(Configuration config) {
//傳回預設實作
return new DefaultSqlSessionFactory(config);
}
public DefaultSqlSessionFactory(Configuration configuration) {
this.configuration = configuration;
}
//到此擷取到了 SqlSessionFactory
//開啟一個會話
SqlSession session = sqlSessionFactory.openSession();
public SqlSession openSession() {
//執行器 預設類型為 simpleExecutor
return openSessionFromDataSource(configuration.getDefaultExecutorType(), null, false);
}
private SqlSession openSessionFromDataSource(
ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
Transaction tx = null;
try {
//擷取加載配置的 環境資訊
final Environment environment = configuration.getEnvironment();
//擷取配置的事務工廠
// jdbc 的JdbcTransactionFactory 容器 的 ManagedTransactionFactory
final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);
//開啟新的事物
tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
//初始化執行器
final Executor executor = configuration.newExecutor(tx, execType);
//傳回預設 sql session 實作
return new DefaultSqlSession(configuration, executor, autoCommit);
} catch (Exception e) {
closeTransaction(tx); // may have fetched a connection so lets call close()
throw ExceptionFactory.wrapException("Error opening session. Cause: " + e, e);
} finally {
ErrorContext.instance().reset();
}
}
//初始化執行期
public Executor newExecutor(Transaction transaction, ExecutorType executorType) {
executorType = executorType == null ? defaultExecutorType : executorType;
executorType = executorType == null ? ExecutorType.SIMPLE : executorType;
Executor executor;
//批量執行器
if (ExecutorType.BATCH == executorType) {
executor = new BatchExecutor(this, transaction);
} else if (ExecutorType.REUSE == executorType) {
executor = new ReuseExecutor(this, transaction);
} else {
executor = new SimpleExecutor(this, transaction);
}
if (cacheEnabled) {
//支援緩存 再包裹一個 CachingExecutor
executor = new CachingExecutor(executor);
}
//鍊式調用
executor = (Executor) interceptorChain.pluginAll(executor);
return executor;
}
SimpleExecutor:每執行一次 update 或 select，就開啟一個 Statement 對象，用 完立刻關閉 Statement 對象。
ReuseExecutor:執行 update 或 select，以 sql 作為 key 查找 Statement 對象， 存在就使用，不存在就建立，用完後，不關閉 Statement 對象，而是放置于 Map 内， 供下一次使用。簡言之，就是重複使用 Statement 對象。
BatchExecutor:執行 update(沒有 select，JDBC 批處理不支援 select)，将所 有 sql 都添加到批進行中(addBatch())，等待統一執行(executeBatch())，它緩存 了多個 Statement 對象，每個 Statement 對象都是 addBatch()完畢後，等待逐一執行 executeBatch()批處理。與 JDBC 批處理相同
//擷取mapper 實際擷取的對象為 mapperProxy
BlogMapper mapper = session.getMapper(BlogMapper.class);
//DefaultSession getMapper 方法
@Override
public <T> T getMapper(Class<T> type) {
return configuration.<T>getMapper(type, this);
}
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
return mapperRegistry.getMapper(type, sqlSession);
}
public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type);
if (mapperProxyFactory == null) {
throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
}
try {
return mapperProxyFactory.newInstance(sqlSession);
} catch (Exception e) {
throw new BindingException("Error getting mapper instance. Cause: " + e, e);
}
}
public T newInstance(SqlSession sqlSession) {
final MapperProxy<T> mapperProxy = new MapperProxy<T>(sqlSession, mapperInterface, methodCache);
return newInstance(mapperProxy);
}
protected T newInstance(MapperProxy<T> mapperProxy) {
return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(),
new Class[] { mapperInterface }, mapperProxy);
}
//具體調用
Blog blog = mapper.selectBlogById(1);
//實際執行為 mapperProxy invoke方法
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
//首先判斷是否需要去執行 SQL，還是直接執行方法。
try {
if (Object.class.equals(method.getDeclaringClass())) {
return method.invoke(this, args);
} else if (isDefaultMethod(method)) {
//是否為預設方法 是 直接調用預設方法
return invokeDefaultMethod(proxy, method, args);
}
} catch (Throwable t) {
throw ExceptionUtil.unwrapThrowable(t);
}
//擷取緩存，儲存了方法簽名和接口方法的關系
final MapperMethod mapperMethod = cachedMapperMethod(method);
return mapperMethod.execute(sqlSession, args);
}
/**
* Backport of java.lang.reflect.Method#isDefault()
*/
private boolean isDefaultMethod(Method method) {
return (method.getModifiers()
& (Modifier.ABSTRACT | Modifier.PUBLIC | Modifier.STATIC)) == Modifier.PUBLIC
&& method.getDeclaringClass().isInterface();
}
//這個是 Java 8 接口中預設方法的示例:
public interface IService { default String getName(){
return "DE";
}
}
//Map 的 computeIfAbsent()方法:隻有 key 不存在或者 value 為 null 的時候才調
//用 mappingFunction()
private MapperMethod cachedMapperMethod(Method method) {
return methodCache.computeIfAbsent(method, k -> new MapperMethod(
mapperInterface, method, sqlSession.getConfiguration()));
}
// 執行 mapperMethod.execute(sqlSession, args);
//MapperMethod 類execute
public Object execute(SqlSession sqlSession, Object[] args) {
Object result;
// 内部類 sqlcommand 屬性 type
switch (command.getType()) {
case INSERT: {
Object param = method.convertArgsToSqlCommandParam(args);
result = rowCountResult(sqlSession.insert(command.getName(), param));
break;
}
case UPDATE: {
Object param = method.convertArgsToSqlCommandParam(args);
result = rowCountResult(sqlSession.update(command.getName(), param));
break;
}
case DELETE: {
Object param = method.convertArgsToSqlCommandParam(args);
result = rowCountResult(sqlSession.delete(command.getName(), param));
break;
}
case SELECT:
//方法傳回值 為void and 方法有結果handler
if (method.returnsVoid() && method.hasResultHandler()) {
executeWithResultHandler(sqlSession, args);
result = null;
} else if (method.returnsMany()) {
//傳回多個結果
result = executeForMany(sqlSession, args);
} else if (method.returnsMap()) {
//傳回 resultMap
result = executeForMap(sqlSession, args);
} else if (method.returnsCursor()) {
//傳回 returnsCursor
result = executeForCursor(sqlSession, args);
} else {
//轉換參數
Object param = method.convertArgsToSqlCommandParam(args);
result = sqlSession.selectOne(command.getName(), param);
if (method.returnsOptional()
&& (result == null || !method.getReturnType().equals(result.getClass()))) {
result = Optional.ofNullable(result);
}
}
break;
case FLUSH:
result = sqlSession.flushStatements();
break;
default:
throw new BindingException("Unknown execution method for: " + command.getName());
}
if (result == null && method.getReturnType().isPrimitive() && !method.returnsVoid()) {
throw new BindingException("Mapper method '" + command.getName()
+ " attempted to return null from a method with a primitive return type (" + method.getReturnType() + ").");
}
return result;
}
//查詢的 類型
//sqlSession.selectOne 執行
//DefaultSqlSession 類中 selectOne
@Override
public <T> T selectOne(String statement, Object parameter) {
// Popular vote was to return null on 0 results and throw exception on too many.
List<T> list = this.selectList(statement, parameter);
if (list.size() == 1) {
return list.get(0);
} else if (list.size() > 1) {
throw new TooManyResultsException("Expected one result (or null) to be returned by selectOne(), but found: " + list.size());
} else {
return null;
}
}
@Override
public <E> List<E> selectList(String statement, Object parameter) {
return this.selectList(statement, parameter, RowBounds.DEFAULT);
}
@Override
public <E> List<E> selectList(String statement, Object parameter, RowBounds rowBounds) {
try {
//從configuration 中擷取 mappedStatements
MappedStatement ms = configuration.getMappedStatement(statement);
//調用執行器 執行查詢 BaseExecutor 的 query() 預設 simpleExecutor 如果使用緩存了 先進入CachingExecutor
return executor.query(ms, wrapCollection(parameter), rowBounds, Executor.NO_RESULT_HANDLER);
} catch (Exception e) {
throw ExceptionFactory.wrapException("Error querying database. Cause: " + e, e);
} finally {
ErrorContext.instance().reset();
}
}
//啟用緩存的情況首先進入 CachingExecutor query()
@Override
public <E> List<E> query(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler) throws SQLException {
BoundSql boundSql = ms.getBoundSql(parameterObject);
CacheKey key = createCacheKey(ms, parameterObject, rowBounds, boundSql);
return query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
}
@Override
public <E> List<E> query(MappedStatement ms, Object parameterObject,
RowBounds rowBounds, ResultHandler resultHandler,
CacheKey key, BoundSql boundSql) throws SQLException {
Cache cache = ms.getCache();
if (cache != null) {
flushCacheIfRequired(ms);
if (ms.isUseCache() && resultHandler == null) {
//使用了緩存 resultHandler 為空
ensureNoOutParams(ms, boundSql);
@SuppressWarnings("unchecked")
List<E> list = (List<E>) tcm.getObject(cache, key);
if (list == null) {
//緩存為空
list = delegate.query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
tcm.putObject(cache, key, list); // issue #578 and #116
}
return list;
}
}
return delegate.query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);
}
//接着往下調用 到BaseExecutor
//BaseExecutor 的 query()
@Override
public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler) throws SQLException {
BoundSql boundSql = ms.getBoundSql(parameter);
//建立緩存key
CacheKey key = createCacheKey(ms, parameter, rowBounds, boundSql);
return query(ms, parameter, rowBounds, resultHandler, key, boundSql);
}
@SuppressWarnings("unchecked")
@Override
public <E> List<E> query(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql) throws SQLException {
ErrorContext.instance()
.resource(ms.getResource())
.activity("executing a query").object(ms.getId());
if (closed) {
throw new ExecutorException("Executor was closed.");
}
if (queryStack == 0 && ms.isFlushCacheRequired()) {
//需要重新整理緩存
//清理本地緩存
clearLocalCache();
}
List<E> list;
try {
queryStack++;
//擷取緩存
list = resultHandler == null ? (List<E>) localCache.getObject(key) : null;
if (list != null) {
//處理本地緩存參數
handleLocallyCachedOutputParameters(ms, key, parameter, boundSql);
} else {
//資料庫查詢
list = queryFromDatabase(ms, parameter, rowBounds, resultHandler, key, boundSql);
}
} finally {
queryStack--;
}
if (queryStack == 0) {
for (DeferredLoad deferredLoad : deferredLoads) {
deferredLoad.load();
}
// issue #601
deferredLoads.clear();
if (configuration.getLocalCacheScope() == LocalCacheScope.STATEMENT) {
// issue #482
clearLocalCache();
}
}
return list;
}
@Override
public void clearLocalCache() {
if (!closed) {
localCache.clear();
localOutputParameterCache.clear();
}
}
private <E> List<E> queryFromDatabase(MappedStatement ms, Object parameter,
RowBounds rowBounds, ResultHandler resultHandler,
CacheKey key, BoundSql boundSql) throws SQLException {
List<E> list;
//先在緩存用占位符占位。執行查詢後，移除占位符，放入資料。
localCache.putObject(key, EXECUTION_PLACEHOLDER);
try {
//實際實作 在 baseExecutor實作類中
list = doQuery(ms, parameter, rowBounds, resultHandler, boundSql);
} finally {
localCache.removeObject(key);
}
localCache.putObject(key, list);
if (ms.getStatementType() == StatementType.CALLABLE) {
localOutputParameterCache.putObject(key, parameter);
}
return list;
}
//simpleExecutor doQuery實作
@Override
public <E> List<E> doQuery(MappedStatement ms,
Object parameter, RowBounds rowBounds,
ResultHandler resultHandler,
BoundSql boundSql) throws SQLException {
Statement stmt = null;
try {
Configuration configuration = ms.getConfiguration();
//建立 statementHandler
StatementHandler handler = configuration.newStatementHandler(wrapper, ms, parameter, rowBounds, resultHandler, boundSql);
//預處理
stmt = prepareStatement(handler, ms.getStatementLog());
return handler.query(stmt, resultHandler);
} finally {
closeStatement(stmt);
}
}
///初始化了一個 statementHandler
public StatementHandler newStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
StatementHandler statementHandler = new RoutingStatementHandler(executor, mappedStatement, parameterObject, rowBounds, resultHandler, boundSql);
statementHandler = (StatementHandler) interceptorChain.pluginAll(statementHandler);
return statementHandler;
}
//RoutingStatementHandler 構造
public RoutingStatementHandler(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
switch (ms.getStatementType()) {
case STATEMENT:
delegate = new SimpleStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
break;
case PREPARED:
// 默 認 是 PREPARED
delegate = new PreparedStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
break;
case CALLABLE:
delegate = new CallableStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);
break;
default:
throw new ExecutorException("Unknown statement type: " + ms.getStatementType());
}
}
//預處理
private Statement prepareStatement(StatementHandler handler, Log statementLog) throws SQLException {
Statement stmt;
Connection connection = getConnection(statementLog);
stmt = handler.prepare(connection, transaction.getTimeout());
//處理參數
handler.parameterize(stmt);
return stmt;
}
//PreparedStatementHandler 類中 parameterize
@Override
public void parameterize(Statement statement) throws SQLException {
parameterHandler.setParameters((PreparedStatement) statement);
}
//PreparedStatementHandler 的query 方法
@Override
public <E> List<E> query(Statement statement, ResultHandler resultHandler) throws SQLException {
PreparedStatement ps = (PreparedStatement) statement;
//猜猜這裡具體執行的類是哪個 沒錯 debug 模式 可以看到是PreparedStatementLogger 最後又調用mysql的
//PreparedStatement 又使用到了代理模式
ps.execute();
return resultSetHandler.handleResultSets(ps);
}
//resultSetHandler 結果處理
//實作類DefaultResultSetHandler handleResultSets
@Override
public List<Object> handleResultSets(Statement stmt) throws SQLException {
ErrorContext.instance().activity("handling results").object(mappedStatement.getId());
final List<Object> multipleResults = new ArrayList<>();
int resultSetCount = 0;
ResultSetWrapper rsw = getFirstResultSet(stmt);
List<ResultMap> resultMaps = mappedStatement.getResultMaps();
int resultMapCount = resultMaps.size();
validateResultMapsCount(rsw, resultMapCount);
while (rsw != null && resultMapCount > resultSetCount) {
ResultMap resultMap = resultMaps.get(resultSetCount);
handleResultSet(rsw, resultMap, multipleResults, null);
rsw = getNextResultSet(stmt);
cleanUpAfterHandlingResultSet();
resultSetCount++;
}
String[] resultSets = mappedStatement.getResultSets();
if (resultSets != null) {
while (rsw != null && resultSetCount < resultSets.length) {
ResultMapping parentMapping = nextResultMaps.get(resultSets[resultSetCount]);
if (parentMapping != null) {
String nestedResultMapId = parentMapping.getNestedResultMapId();
ResultMap resultMap = configuration.getResultMap(nestedResultMapId);
handleResultSet(rsw, resultMap, null, parentMapping);
}
rsw = getNextResultSet(stmt);
cleanUpAfterHandlingResultSet();
resultSetCount++;
}
}
return collapseSingleResultList(multipleResults);
}
private List<Object> collapseSingleResultList(List<Object> multipleResults) {
return multipleResults.size() == 1 ? (List<Object>) multipleResults.get(0) : multipleResults;
}
查到到對應結果進行傳回
到此基本已經結束 ，歡迎多批評指教
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