MyBatis (四) 最佳实际

2024-04-27 15:17:16

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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：这里写图片描述

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">  <insert id="insertReteunId" parameterType="com.zll.mybatis.bean.User"> <selectKey keyProperty="id" order="AFTER" resultType="int">  select last_insert_id(); </selectKey> insert into user(parentId,sonId,name,birthday) value(#{parentId},#{sonId},#{name},#{birthday}) </insert>  <delete id="deleteById" parameterType="int"> delete from user where id=#{id} </delete>  <update id="updateById" parameterType="com.zll.mybatis.bean.User"> update user set parentId=#{parentId},sonId=#{sonId},name=#{name},birthday=#{birthday} where id=#{id} </update>  <select id="findByName" parameterType="string" resultType="com.zll.mybatis.bean.User">  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>  <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(); }}

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