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)