JavaBeans的设计和实现
（一）DataConvert类是一个工具类，实现string，date,int三种数据类型的相互转换，为后续的编程提供便利。详情如下：
package hrims.util;//打包的相对地址
import java.util.*;//引用系统类
import java.text.*;//引用系统类
import java.io.*;
//以上内容后续每个类都会有，相同的内容均不再重复介绍！
public class DataConvert {
public DataConvert(){}
// 此方法实现了将当前日期（格式：yyyy-MM-dd）转换为String类型
public static String getStringDate()
{
java.util.Date currentTime = new java.util.Date();
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
String dateString = formatter.format(currentTime);
return dateString;
}
/*说明：
Java.sql.Date和Java.util.Date的区别：
Java.sql.Date是Java.util.Date的子类
Java.util.Date：可以包含年月日时分秒
Java.sql.Date：只能有年月日*/
//此方法实现了将String类型转换为数据库Date类型
public static java.sql.Date StrTosqlDate(String strDate)
{
if(strDate==null || strDate=="")
strDate = "1980-01-01";
return java.sql.Date.valueOf(strDate.substring(0, 10));
}
//此方法实现了将数据库Date类型转换为String类型
public static String sqlDateToStr(java.sql.Date dateDate)
{
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
String dateString = formatter.format(dateDate);
return dateString;
}
//此方法实现了将String类型转换为int类型
public static int StrToInt(String str)
{
if(str==null || str == "")
return 0;
return Integer.parseInt(str);
}
//此方法实现了将int类型转换为String类型
public static String IntToStr(int i)
{
return String.valueOf(i);
}
//此方法实现了将空字符串赋值特定值
public static String ViewStr(String str)
{
if (str.equals(""))
return "空";
else
return str;
}
}
（二）DBConnect和DBConnectionManager类，用于实现数据库连接。详情如下：
package hrims.database;
import java.io.*;
import java.sql.*;
import java.util.*;
import java.util.Date;
public class DBConnectionManager {
static private DBConnectionManager instance; // 唯一实例
static private int clients;
private Vector drivers = new Vector();
private Hashtable pools = new Hashtable();
/**
* 将文本信息在后台打印出来
*/
private void log(String msg) {
System.out.println(new Date() + ": " + msg);
}
/*
* 返回唯一实例.如果是第一次调用此方法,则创建实例
*
* @return DBConnectionManager 唯一实例
*/
static synchronized public DBConnectionManager getInstance() {
if (instance == null) {
instance = new DBConnectionManager();
}
clients++;
return instance;
}
/**
* 建构函数私有以防止其它对象创建本类实例
*/
private DBConnectionManager() {
init();
}
/**
* 将连接对象返回给由名字指定的连接池
*
* @param name
* 在属性文件中定义的连接池名字
* @param con
* 连接对象
*/
public void freeConnection(String name, Connection con) {
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null) {
pool.freeConnection(con);
}
}
/**
* 获得一个可用的(空闲的)连接.如果没有可用连接,且已有连接数小于最大连接数 限制,则创建并返回新连接
*
* @param name
* 在属性文件中定义的连接池名字
* @return Connection 可用连接或null
*/
public Connection getConnection(String name) {
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null) {
return pool.getConnection();
}
return null;
}
/**
* 获得一个可用连接.若没有可用连接,且已有连接数小于最大连接数限制, 则创建并返回新连接.否则,在指定的时间内等待其它线程释放连接.
*
* @param name
* 连接池名字
* @param time
* 以毫秒计的等待时间
* @return Connection 可用连接或null
*/
public Connection getConnection(String name, long time) {
DBConnectionPool pool = (DBConnectionPool) pools.get(name);
if (pool != null) {
return pool.getConnection(time);
}
return null;
}
/**
* 关闭所有连接,撤销驱动程序的注册
*/
public synchronized void release() {
// 等待直到最后一个客户程序调用
if (--clients != 0) {
return;
}
Enumeration allPools = pools.elements();
while (allPools.hasMoreElements()) {
DBConnectionPool pool = (DBConnectionPool) allPools.nextElement();
pool.release();
}
Enumeration allDrivers = drivers.elements();
while (allDrivers.hasMoreElements()) {
Driver driver = (Driver) allDrivers.nextElement();
try {
DriverManager.deregisterDriver(driver);
log("撤销JDBC驱动程序 " + driver.getClass().getName() + "的注册");
} catch (SQLException e) {
log("无法撤销下列JDBC驱动程序的注册: " + driver.getClass().getName());
}
}
}
/**
* 根据指定属性创建连接池实例.
*
* @param props
* 连接池属性
*/
private void createPools(Properties props) {
Enumeration propNames = props.propertyNames();
while (propNames.hasMoreElements()) {
String name = (String) propNames.nextElement();
if (name.endsWith(".url"))
{
String poolName = "sqlserver";
String url = props.getProperty(poolName + ".url");
if (url == null)
{
log("没有为连接池" + poolName + "指定URL");
continue;
}
String user = props.getProperty(poolName + ".user");
String password = props.getProperty(poolName + ".password");
String maxconn = props.getProperty(poolName + ".maxconn", "0");
int max;
try {
max = Integer.valueOf(maxconn).intValue();
} catch (NumberFormatException e) {
log("错误的最大连接数限制: " + maxconn + " .连接池: " + poolName);
max = 0;
}
DBConnectionPool pool = new DBConnectionPool(poolName, url,
user, password, max);
pools.put(poolName, pool);
log("成功创建连接池" + poolName);
}
}
}
/**
* 读取属性完成初始化
*/
private void init() {
InputStream is = getClass().getResourceAsStream("/hrims.txt");
Properties dbProps = new Properties();
try {
dbProps.load(is);
} catch (Exception e) {
log("不能读取属性文件.请确保db.properties在CLASSPATH指定的路径中");
return;
}
loadDrivers(dbProps);
createPools(dbProps);
}
/**
* 装载和注册所有JDBC驱动程序
*
* @param props
* 属性
*/
private void loadDrivers(Properties props) {
String driverClasses = props.getProperty("driver");
StringTokenizer st = new StringTokenizer(driverClasses);
while (st.hasMoreElements()) {
String driverClassName = st.nextToken().trim();
try {
Driver driver = (Driver) Class.forName(driverClassName)
.newInstance();
DriverManager.registerDriver(driver);
drivers.addElement(driver);
log("成功注册JDBC驱动程序" + driverClassName);
} catch (Exception e) {
log("无法注册JDBC驱动程序: " + driverClassName + ", 错误: " + e);
}}}
/**
* 此内部类定义了一个连接池.它能够根据要求创建新连接,直到预定的最大连接数为止.在返回连接给客户程序之前,它能够验证连接的有效性.
*/
class DBConnectionPool {
private int userCount;
private Vector freeConnections = new Vector();
private int maxConn;
private String name;
private String password;
private String URL;
private String user;
/**
* 创建新的连接池
*
* @param name
* 连接池名字
* @param URL
* 数据库的JDBC URL
* @param user
* 数据库帐号,或 null
* @param password
* 密码,或 null
* @param maxConn
* 此连接池允许建立的最大连接数
*/
public DBConnectionPool(String name, String URL, String user,
String password, int maxConn) {
this.name = name;
this.URL = URL;
this.user = user;
this.password = password;
this.maxConn = maxConn;
}
/**
* 将不再使用的连接返回给连接池
*
* @param con
* 客户程序释放的连接
*/
public synchronized void freeConnection(Connection con) {
// 将指定连接加入到向量末尾
freeConnections.addElement(con);
userCount--;
notifyAll();
}
/**
* 从连接池获得一个可用连接.如没有空闲的连接且当前连接数小于最大连接 数限制,则创建新连接.如原来登记为可用的连接不再有效,则从向量删除之,
* 然后递归调用自己以尝试新的可用连接.
*/
public synchronized Connection getConnection() {
Connection con = null;
if (freeConnections.size() > 0) {
// 获取向量中第一个可用连接
con = (Connection) freeConnections.firstElement();
freeConnections.removeElementAt(0);
try {
if (con.isClosed()) {
log("从连接池" + name + "删除一个无效连接");
// 递归调用自己,尝试再次获取可用连接
con = getConnection();
}
} catch (SQLException e) {
log("从连接池" + name + "删除一个无效连接");
// 递归调用自己,尝试再次获取可用连接
con = getConnection();
}
} else if (maxConn == 0 || userCount < maxConn) {
con = newConnection();
}
if (con != null) {
userCount++;
}
return con;
}
/**
* 从连接池获取可用连接.可以指定客户程序能够等待的最长时间 参见前一个getConnection()方法.
*
* @param timeout
* 以毫秒计的等待时间限制
*/
public synchronized Connection getConnection(long timeout) {
long startTime = new Date().getTime();
Connection con;
while ((con = getConnection()) == null) {
try {
wait(timeout);
} catch (InterruptedException e) {
}
if ((new Date().getTime() - startTime) >= timeout) {
// wait()返回的原因是超时
return null;
}}
return con;
}
/**
* 关闭所有连接
*/
public synchronized void release() {
Enumeration allConnections = freeConnections.elements();
while (allConnections.hasMoreElements()) {
Connection con = (Connection) allConnections.nextElement();
try {
con.close();
log("关闭连接池" + name + "中的一个连接");
} catch (SQLException e) {
log("无法关闭连接池" + name + "中的连接");
}}
freeConnections.removeAllElements();
}
/**
* 创建新的连接
*/
private Connection newConnection() {
Connection con = null;
try {
if (user == null) {
con = DriverManager.getConnection(URL);
} else {
con = DriverManager.getConnection(URL, user, password);
}
log("连接池" + name + "创建一个新的连接");
} catch (SQLException e) {
log("无法创建下列URL的连接: " + URL);
return null;
}
return con;
}}}
package hrims.database;
import java.sql.*;
import hrims.database.DBConnectionManager;
public class DBConnect {
private Connection conn = null;
private Statement stmt = null;
private PreparedStatement prepstmt = null;
private DBConnectionManager dcm = null;
void init() {
dcm = DBConnectionManager.getInstance();
conn = dcm.getConnection("sqlserver");
}
/**
* 构造数据库的连接和访问类
*/
public DBConnect() throws Exception {
init();
stmt = conn.createStatement();
}
public DBConnect(int resultSetType, int resultSetConcurrency)
throws Exception {
init();
stmt = conn.createStatement(resultSetType, resultSetConcurrency);
}
/**
* 构造数据库的连接和访问类 预编译SQL语句
*
* @param sql
* SQL语句
*/
public DBConnect(String sql) throws Exception {
init();
this.prepareStatement(sql);
}
public DBConnect(String sql, int resultSetType, int resultSetConcurrency)
throws Exception {
init();
this.prepareStatement(sql, resultSetType, resultSetConcurrency);
}
/**
* 返回连接
*
* @return Connection 连接
*/
public Connection getConnection() {
return conn;
}
/**
* PreparedStatement
*
* @param sql 预设SQL语句
*/
public void prepareStatement(String sql) throws SQLException {
prepstmt = conn.prepareStatement(sql);
}
public void prepareStatement(String sql, int resultSetType,
int resultSetConcurrency) throws SQLException {
prepstmt = conn.prepareStatement(sql, resultSetType,
resultSetConcurrency);
}
/**
* 设置对应值
*
* @param index
* 参数索引
* @param value
* 对应值
*/
public void setString(int index, String value) throws SQLException {
prepstmt.setString(index, value);
}
public void setInt(int index, int value) throws SQLException {
prepstmt.setInt(index, value);
}
public void setBoolean(int index, boolean value) throws SQLException {
prepstmt.setBoolean(index, value);
}
public void setDate(int index, Date value) throws SQLException {
prepstmt.setDate(index, value);
}
public void setTimestamp(int index, Timestamp value) throws SQLException {
prepstmt.setTimestamp(index, value);
}
public void setLong(int index, long value) throws SQLException {
prepstmt.setLong(index, value);
}
public void setFloat(int index, float value) throws SQLException {
prepstmt.setFloat(index, value);
}
public void setBytes(int index, byte[] value) throws SQLException {
prepstmt.setBytes(index, value);
}
public void clearParameters() throws SQLException {
prepstmt.clearParameters();
prepstmt = null;
}
/**
* 返回预设状态
*/
public PreparedStatement getPreparedStatement() {
return prepstmt;
}
/**
* 返回状态
*
* @return Statement 状态
*/
public Statement getStatement() {
return stmt;
}
/**
* 执行SQL语句返回字段集
*
* @param sql
* SQL语句
* @return ResultSet 字段集
*/
public ResultSet executeQuery(String sql) throws SQLException {
if (stmt != null) {
return stmt.executeQuery(sql);
} else
return null;
}
public ResultSet executeQuery() throws SQLException {
if (prepstmt != null) {
return prepstmt.executeQuery();
} else
return null;
}
/**
* 执行SQL语句
*
* @param sql
* SQL语句
*/
public void executeUpdate(String sql) throws SQLException {
if (stmt != null)
stmt.executeUpdate(sql);
}
public void executeUpdate() throws SQLException {
if (prepstmt != null)
prepstmt.executeUpdate();
}
/**
* 关闭连接
*/
public void close() throws Exception {
if (stmt != null) {
stmt.close();
stmt = null;
}
if (prepstmt != null) {
prepstmt.close();
prepstmt = null;
}
if (conn != null) {dcm.freeConnection("sqlserver", conn);
}}}
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