MyBatis(2)：CRUD操作

编写接口

import com.shandx.pojo.User;
import java.util.List;
public interface UserMapper {
<span class="hljs-comment">//获取全部的用户</span>
<span class="hljs-function">List&lt;User&gt; <span class="hljs-title">selectUser</span><span class="hljs-params">()</span></span>;

<span class="hljs-comment">//通过id查找用户</span>
<span class="hljs-function">User <span class="hljs-title">selectUserById</span><span class="hljs-params">(<span class="hljs-keyword">int</span> id)</span></span>;

<span class="hljs-comment">//增加用户</span>
<span class="hljs-function"><span class="hljs-keyword">int</span> <span class="hljs-title">addUser</span><span class="hljs-params">(User user)</span></span>;

<span class="hljs-comment">//通过id删除用户</span>
<span class="hljs-function"><span class="hljs-keyword">int</span> <span class="hljs-title">deleteUserById</span><span class="hljs-params">(<span class="hljs-keyword">int</span> id)</span></span>;

<span class="hljs-comment">//更新用户</span>
<span class="hljs-function"><span class="hljs-keyword">int</span> <span class="hljs-title">updateUser</span><span class="hljs-params">(User user)</span></span>;

}

对应的mapper语句编写

<?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标签的namespace对应Mapper接口的类-->

<mapper namespace="com.shandx.dao.UserMapper">
<span class="hljs-comment">&lt;!--select标签的id对应映射接口的方法名字  resultType:返回结果的类型  中间就编写sql语句--&gt;</span>
<span class="hljs-comment">&lt;!--获取全部的用户--&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">select</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"selectUser"</span> <span class="hljs-attr">resultType</span>=<span class="hljs-string">"com.shandx.pojo.User"</span>&gt;</span>
    select * from user
<span class="hljs-tag">&lt;/<span class="hljs-name">select</span>&gt;</span>

<span class="hljs-comment">&lt;!--通过id查找用户--&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">select</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"selectUserById"</span> <span class="hljs-attr">resultType</span>=<span class="hljs-string">"com.shandx.pojo.User"</span>&gt;</span>
    select *from user where id=#{id}
<span class="hljs-tag">&lt;/<span class="hljs-name">select</span>&gt;</span>

<span class="hljs-comment">&lt;!--增加用户--&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">insert</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"addUser"</span> <span class="hljs-attr">parameterType</span>=<span class="hljs-string">"com.shandx.pojo.User"</span>&gt;</span>
    insert into user (id,name,pwd) values (#{id},#{name},#{pwd})
<span class="hljs-tag">&lt;/<span class="hljs-name">insert</span>&gt;</span>

<span class="hljs-comment">&lt;!--通过id删除用户--&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">delete</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"deleteUserById"</span> <span class="hljs-attr">parameterType</span>=<span class="hljs-string">"com.shandx.pojo.User"</span>&gt;</span>
    delete from user where id=#{id}
<span class="hljs-tag">&lt;/<span class="hljs-name">delete</span>&gt;</span>

<span class="hljs-comment">&lt;!--更新用户--&gt;</span>
<span class="hljs-tag">&lt;<span class="hljs-name">update</span> <span class="hljs-attr">id</span>=<span class="hljs-string">"updateUser"</span> <span class="hljs-attr">parameterType</span>=<span class="hljs-string">"com.shandx.pojo.User"</span>&gt;</span>
    update user set name=#{name},pwd=#{pwd} where id=#{id}
<span class="hljs-tag">&lt;/<span class="hljs-name">update</span>&gt;</span>

</mapper>

测试类

import com.shandx.dao.UserMapper;
import com.shandx.pojo.User;
import com.shandx.utils.MyBatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.junit.Test;
import java.util.List;
public class UserMapperTest {

@Test  //获取全部的用户

public void selectUser() {

//1.拿到sqlSessionFactory对象

SqlSessionFactory sqlSessionFactory = MyBatisUtils.getSqlSessionFactory();

//2.通过sqlSessionFactory对象openSession()创建一个sqlSession。

SqlSession sqlSession = sqlSessionFactory.openSession();

//3.通过sqlSession获得mapper对象 ， 参数为映射文件对应的接口类的class对象

UserMapper mapper = sqlSession.getMapper(UserMapper.class);

//4.通过mapper对象来执行操作；

List<User> users = mapper.selectUser();

//获得结果集

for (User user : users) {

System.out.println(user);

}

}
<span class="hljs-meta">@Test</span> <span class="hljs-comment">//通过id查找用户</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> selectUserById(){
    SqlSessionFactory sqlSessionFactory = MyBatisUtils.getSqlSessionFactory();
    SqlSession sqlSession = sqlSessionFactory.openSession();
    UserMapper mapper = sqlSession.getMapper(UserMapper.<span class="hljs-keyword">class</span>);

    User user = mapper.selectUserById(<span class="hljs-number">2</span>);
    System.out.println(user);
}

<span class="hljs-meta">@Test</span>    <span class="hljs-comment">//增加用户</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> addUser(){
    SqlSessionFactory sqlSessionFactory = MyBatisUtils.getSqlSessionFactory();
    SqlSession sqlSession = sqlSessionFactory.openSession();
    UserMapper mapper = sqlSession.getMapper(UserMapper.<span class="hljs-keyword">class</span>);

    User user = <span class="hljs-keyword">new</span> User(<span class="hljs-number">5</span>, <span class="hljs-string">"shandianxia"</span>, <span class="hljs-string">"521"</span>);
    <span class="hljs-keyword">int</span> i = mapper.addUser(user);
    <span class="hljs-keyword">if</span>(i&gt;<span class="hljs-number">0</span>){
        System.out.println(<span class="hljs-string">"插入成功！！！"</span>);
    }
    sqlSession.commit();<span class="hljs-comment">//提交事务</span>
    sqlSession.close();<span class="hljs-comment">//关闭</span>
}

<span class="hljs-meta">@Test</span> <span class="hljs-comment">//通过id删除用户</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> deleteUserById(){
    SqlSessionFactory sqlSessionFactory = MyBatisUtils.getSqlSessionFactory();
    SqlSession sqlSession = sqlSessionFactory.openSession();
    UserMapper mapper = sqlSession.getMapper(UserMapper.<span class="hljs-keyword">class</span>);

    <span class="hljs-keyword">int</span> i = mapper.deleteUserById(<span class="hljs-number">5</span>);
    <span class="hljs-keyword">if</span>(i&gt;<span class="hljs-number">0</span>){
        System.out.println(<span class="hljs-string">"删除成功！！！"</span>);
    }
    sqlSession.commit();<span class="hljs-comment">//提交事务</span>
    sqlSession.close();<span class="hljs-comment">//关闭</span>
}

<span class="hljs-meta">@Test</span> <span class="hljs-comment">//更新用户</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> updateUser(){
    SqlSessionFactory sqlSessionFactory = MyBatisUtils.getSqlSessionFactory();
    SqlSession sqlSession = sqlSessionFactory.openSession();
    UserMapper mapper = sqlSession.getMapper(UserMapper.<span class="hljs-keyword">class</span>);

    User user = <span class="hljs-keyword">new</span> User(<span class="hljs-number">3</span>, <span class="hljs-string">"雷神"</span>, <span class="hljs-string">"456"</span>);
    <span class="hljs-keyword">int</span> i = mapper.updateUser(user);
    <span class="hljs-keyword">if</span>(i&gt;<span class="hljs-number">0</span>){
        System.out.println(<span class="hljs-string">"更新成功！！！"</span>);
    }
    sqlSession.commit();<span class="hljs-comment">//提交事务</span>
    sqlSession.close();
}

}

总结CRUD注意点

1，增删改查需要提交事务
2，如果出现乱码，先在sql中进行测试，sql没问题，就检查配置文件

jdbc:mysql://localhost:3306/mybatis?
useSSL=true&useUnicode=true&characterEncoding=utf-8"

3，如果是基本数据类型，可以省略，但建议写上，引用类型必须写指定的 包名+类名