1.定義 Table 注解
package test;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Inherited
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Table {
String value() default "";
}
2.定義 Column 注解
@Target({ElementType.FIELD})
public @interface Column {
3.定義使用注解的實體
@Table("tb_test")
public class TestDto {
@Deprecated
private String tt;
@Column("_id")
private String id;
@Column("username")
private String name;
public TestDto(String id, String name) {
super();
this.id = id;
this.name = name;
}
public String getId() {
return id;
public void setId(String id) {
public String getName() {
return name;
public void setName(String name) {
4.測試注解
import java.lang.reflect.Field;
import java.lang.reflect.Method;
public class Test {
public static void main(String[] args) {
TestDto testDto = new TestDto("123", "34");
TestDto testDto1 = new TestDto("123", "test1");
TestDto testDto2 = new TestDto("", "test1,test2,test3,test4");
String sql = assembleSqlFromObj(testDto);
String sql1 = assembleSqlFromObj(testDto1);
String sql2 = assembleSqlFromObj(testDto2);
System.out.println(sql);
System.out.println(sql1);
System.out.println(sql2);
/**
* 通過注解來組裝查詢條件,生成查詢語句
*
* @param obj
* @return
*/
public static String assembleSqlFromObj(Object obj) {
Table table = obj.getClass().getAnnotation(Table.class);
StringBuffer sbSql = new StringBuffer();
String tableName = table.value();
sbSql.append("select * from " + tableName + " where 1=1 ");
Field[] fileds = obj.getClass().getDeclaredFields();
for (Field f : fileds) {
String fieldName = f.getName();
String methodName = "get" + fieldName.substring(0, 1).toUpperCase()
+ fieldName.substring(1);
try {
Column column = f.getAnnotation(Column.class);
if (column != null) {
Method method = obj.getClass().getMethod(methodName);
String value = (String) method.invoke(obj);
if (value != null && !value.equals("")) {
if (!isNum(column.value()) && !isNum(value)) {
// 判斷參數是不是 in 類型參數 1,2,3
if (value.contains(",")) {
sbSql.append(" and " + column.value() + " in (" + value + ") ");
} else {
sbSql.append(" and " + column.value() + " like '%" + value + "%' ");
}
} else {
sbSql.append(" and " + column.value() + "=" + value + " ");
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
return sbSql.toString();
* 檢查給定的值是不是 id 類型 1.檢查字段名稱 2.檢查字段值
* @param target
public static boolean isNum(String target) {
boolean isNum = false;
if (target.toLowerCase().contains("id")) {
isNum = true;
if (target.matches("\\d+")) {
return isNum;
測試結果:
select * from tb_test where 1=1 and _id=123 and username=34
select * from tb_test where 1=1 and _id=123 and username like '%test1%'
select * from tb_test where 1=1 and username in (test1,test2,test3,test4)