MyBatis (四) 最佳实际

到看这里，现在在返回第一章，hibernate 和 mybatis的区别，是否感觉更加深刻了。

下面我们进入我们本章的重点：
mybatis 实际应用中按照下面的4个步骤：
- 创建实体对象 （User.java）
- 创建操作数据库接口 (UserDao.java)
- 用mapper 完成接口实现 （UserDao.xml） 重点（通过mapper 映射就可以直接调用接口）
- 配置映射文件包（在mybatis-config.xml中配置）

下面是代码：

User.java 代码

package com.zll.mybatis.bean;import java.util.Date;public class User {    private int id;    private int parentId;    private int sonId;    private String name;    private Date birthday;    public int getId() {        return id;    }    public void setId(int id) {        this.id = id;    }    public int getParentId() {        return parentId;    }    public void setParentId(int parentId) {        this.parentId = parentId;    }    public int getSonId() {        return sonId;    }    public void setSonId(int sonId) {        this.sonId = sonId;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public Date getBirthday() {        return birthday;    }    public void setBirthday(Date birthday) {        this.birthday = birthday;    }    @Override    public String toString() {        return "User [id=" + id + ", parentId=" + parentId + ", sonId=" + sonId + ", name=" + name + ", birthday=" + birthday + "]";    }}

UserDao 代码

package com.zll.mybatis.dao;import java.util.List;import com.zll.mybatis.bean.User;public interface UserDao {    public void insertReteunId(User user) throws Exception;    public void deleteById(int id) throws Exception;    public void updateById(User user) throws Exception;    public List<User> findByName(String username) throws Exception;}

UserDao.xml 代码 （核心，实现了UserDao的接口）

这里必须做到4个一致：
1、namespace 和 映射对象 包名类名一致。
2、id名称 和 映射对象 方法名 一致
3、parameterType 和 映射对象 参数类型 一致
4、resultType 和 映射对象 返回类型 一致

<?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="com.zll.mybatis.dao.UserDao">    <!-- 增加用户并返回 id-->    <insert id="insertReteunId" parameterType="com.zll.mybatis.bean.User">        <selectKey keyProperty="id" order="AFTER" resultType="int">            <!-- sql语句，获取最近插入数据的id -->            select last_insert_id();        </selectKey>        insert into user(parentId,sonId,name,birthday) value(#{parentId},#{sonId},#{name},#{birthday})    </insert>    <!-- 删除 -->    <delete id="deleteById" parameterType="int">        delete from user where id=#{id}    </delete>    <!-- 更新 -->    <update id="updateById" parameterType="com.zll.mybatis.bean.User">        update user set parentId=#{parentId},sonId=#{sonId},name=#{name},birthday=#{birthday} where id=#{id}    </update>     <!-- 模糊查询     ${}符号表示sql使用拼接方式，这样会参数sql注入露点，所以大家要注意 -->    <select id="findByName" parameterType="string" resultType="com.zll.mybatis.bean.User">        <!-- select * from user where name like "%${value}%" -->        select * from user where name like #{value}    </select></mapper>

最后在在mybatis-config.xml中添加映射路径：

<?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>  <environments default="development">    <environment id="development">      <transactionManager type="JDBC"/>      <dataSource type="POOLED">        <property name="driver" value="com.mysql.jdbc.Driver"/>        <property name="url" value="jdbc:mysql://localhost:3306/my_db?characterEncoding=UTF8"/>        <property name="username" value="root"/>        <property name="password" value="root"/>      </dataSource>    </environment>  </environments>  <mappers>    <!-- 映射路径  添加整个包，就不用每个类都配置了 -->    <package name="com/zll/mybatis/dao"/>  </mappers></configuration>

测试代码（直接调用接口完成数据查询）：

package com.zll.mybatis.mybatis;import java.io.InputStream;import java.util.Date;import java.util.List;import junit.framework.TestCase;import org.apache.ibatis.io.Resources;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;import com.zll.mybatis.bean.User;import com.zll.mybatis.dao.UserDao;/** * Unit test for simple App. */public class AppTest extends TestCase {    SqlSessionFactory sqlSessionFactory;    @Override    protected void setUp() throws Exception {        super.setUp();        String resource = "mybatis-config.xml";        InputStream inputStream = Resources.getResourceAsStream(resource);        sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);    }    public void insertUser() throws Exception {        SqlSession session = sqlSessionFactory.openSession();        UserDao mapper = session.getMapper(UserDao.class);        User user = new User();        user.setName("小红萝卜");        user.setBirthday(new Date());        mapper.insertReteunId(user);        System.out.println("user id = "+user.getId());        session.close();    }    public void updateUser() throws Exception {        SqlSession session = sqlSessionFactory.openSession();        UserDao mapper = session.getMapper(UserDao.class);        User user = new User();        user.setId(4);        user.setParentId(3);        user.setName("小狗蛋");        user.setBirthday(new Date());        mapper.updateById(user);        session.commit();        session.close();    }    public void findUser() throws Exception {        SqlSession session = sqlSessionFactory.openSession();        UserDao mapper = session.getMapper(UserDao.class);        List<User> list = mapper.findByName("%小%");        for(int i=0; i<list.size(); i++){            System.out.println(list.get(i));        }        session.close();    }    public void deleteUser() throws Exception {        SqlSession session = sqlSessionFactory.openSession();        UserDao mapper = session.getMapper(UserDao.class);        mapper.deleteById(8);        session.commit();        session.close();    }}