利用java反射、注解及泛型模拟ORM实现
/**
* org.crazystone.annotation
*
* Function： TODO
*
* ver date author
* ──────────────────────────────────
* 2012-9-11 zhangzenglun
*
* Copyright (c) 2012, TNT All Rights Reserved.
*/
package org.crazystone.annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
*
* @author zhangzenglun
* @version 1.0
* @since v1.0
* @Date 2012-9-11 下午2:06:08
*/
/**
* @Retention用来声明注解的保留策略，有CLASS、RUNTIME和SOURCE这三种，分别表示注解保存在类文件、JVM运行时刻和源代码中。
* 只有当声明为RUNTIME的时候，才能够在运行时刻通过反射API来获取到注解的信息。
*
* @Target用来声明注解可以被添加在哪些类型的元素上，如类型、方法和域等
*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface Table {
String tableName();
}
/**
* TableField.java
* org.crazystone.annotation
*
* Function： TODO
*
* ver date author
* ──────────────────────────────────
* 2012-9-11 zhangzenglun
*
* Copyright (c) 2012, TNT All Rights Reserved.
*/
package org.crazystone.annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
/**
* ClassName:TableField
*
* @author zhangzenglun
* @version 1.0
* @since v1.0
* @Date 2012-9-11 下午2:14:41
*/
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.FIELD,ElementType.METHOD})
public @interface TableField {
public String name();
public boolean isPrimaryKey() default false;
}
/**
* User.java
* org.crazystone.annotation
*
* Function： TODO
*
* ver date author
* ──────────────────────────────────
* 2012-9-11 zhangzenglun
*
* Copyright (c) 2012, TNT All Rights Reserved.
*/
package org.crazystone.annotation;
/**
* ClassName:User
*
* @author zhangzenglun
* @version 1.0
* @since v1.0
* @Date 2012-9-11 下午2:01:06
*/
@Table(tableName = "user")
public class User {
@TableField(name = "user_id", isPrimaryKey = true)
private int userId;
@TableField(name = "user_name")
private String userName;
@TableField(name = "user_age")
private int age;
public int getUserId() {
return userId;
}
public void setUserId(int userId) {
this.userId = userId;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
/**
* BaseOrmSupport.java
* org.crazystone.annotation
*
* Function： TODO
*
* ver date author
* ──────────────────────────────────
* 2012-9-11 zhangzenglun
*
* Copyright (c) 2012, TNT All Rights Reserved.
*/
package org.crazystone.annotation;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
/**
* ClassName:BaseOrmSupport
*
* @author zhangzenglun
* @version 1.0
* @since v1.0
* @Date 2012-9-11 下午3:27:00
*/
public abstract class BaseOrmSupport<T> {
public void save(T o){
Class<? extends Object> entityClass = o.getClass();
StringBuffer sql = new StringBuffer();
sql.append("insert into ");
Table a = (Table)entityClass.getAnnotation(Table.class);
if (a!=null) {
sql.append(a.tableName());
} else {
sql.append(entityClass.getName().substring(entityClass.getName().lastIndexOf(".")+1));
}
sql.append(" (");
Field[] fields = entityClass.getDeclaredFields();
String temp = "";
StringBuffer valueSql = new StringBuffer();
for (Field f:fields) {
TableField tf = f.getAnnotation(TableField.class);
//获得字段第一个字母大写
String firstLetter = f.getName().substring(0,1).toUpperCase();
//转换成字段的get方法
String getMethodName = "get"+firstLetter+f.getName().substring(1);
try {
Method getMethod = entityClass.getMethod(getMethodName, new Class[] {});
//这个对象字段get方法的值
Object value = getMethod.invoke(o, new Object[] {});
if (f.getType().getName().equals(java.lang.String.class.getName())) {
valueSql.append(temp+"'"+value+"'");
} else {
valueSql.append(temp+value);
}
} catch (Exception e) {
}
if (tf != null) {
sql.append(temp+tf.name());
} else {
sql.append(temp+f.getName());
}
temp = ",";
}
sql.append(")values(");
sql.append(valueSql);
sql.append(")");
System.out.println(sql.toString());
}
}
/**
* User.java
* org.crazystone.annotation
*
* Function： TODO
*
* ver date author
* ──────────────────────────────────
* 2012-9-11 zhangzenglun
*
* Copyright (c) 2012, TNT All Rights Reserved.
*/
package org.crazystone.annotation;
/**
* ClassName:User
*
* @author zhangzenglun
* @version 1.0
* @since v1.0
* @Date 2012-9-11 下午2:01:06
*/
public class UserDAO extends BaseOrmSupport<User>{
}
测试类
package org.crazystone.annotation;
import junit.framework.TestCase;
public class AppTest
extends TestCase
{
public void testApp()
{
User user = new User();
user.setAge(100);
user.setUserName("skylun");
user.setUserId(1);
UserDAO userDao = new UserDAO();
userDao.save(user);
}
}
测试输出结果：
insert into user (user_id,user_name,user_age)values(1,'skylun',100)