mybatis的使用及详解

Posted 2020-09-12

一、Mybatis介绍

　　MyBatis是一个支持普通SQL查询，存储过程和高级映射的优秀持久层框架。MyBatis消除了几乎所有的JDBC代码和参数的手工设置以及对结果集的检索封装。MyBatis可以使用简单的XML或注解用于配置和原始映射，将接口和Java的POJO（Plain Old Java Objects，普通的Java对象）映射成数据库中的记录。

二、准备开发环境

　　导入jar包

　　【mybatis】

　　

　　【oracle】

　　

　　生成数据库

　　

三、使用MyBatis查询表中的数据

　　1、添加Mybatis的配置文件conf.xml

　　在src目录下创建一个mybatis.xml文件，如下图所示：

 　　

　　

<?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>
    <properties resource="db.properties"></properties>
    
    <!-- 定义一个别名们 -->
    <typeAliases>
        <!-- <typeAlias type="com.model.TestId" alias="a"/> -->
        <package name="com.model"/>
    </typeAliases> 
  <!-- mybatis的环境们 -->
  <environments default="test">
      <environment id="test">
          <!-- mybatis支持的事务
              JDBC：数据源自己的事务管理
              MANAGE(托管),不支持tomcat，一般用在大型的商业服务器，weblogic,jboss
           -->
          <transactionManager type="JDBC"></transactionManager>
          
          <!-- 数据源链接类型：PLOOLED,UNOOLED,JNDI
              POOLED：连接池
              JJNDI：使用应用服务器的数据源连接
           -->
          <dataSource type="POOLED">
              <property name="driver" value="${driver}"/>
              <property name="url" value="${url}"/>
              <property name="username" value="${username}"/>
              <property name="password" value="${password}"/>
          </dataSource>
      </environment>
      <!-- <environment id="test1">
          
      </environment>
      <environment id="test2">
          
      </environment> -->
  </environments>
  <mappers>
      <mapper resource="com/dao/UsersMapper.xml"/>
  </mappers>
</configuration>

　　db.properties文件如下：

driver=oracle.jdbc.OracleDriver
url=jdbc:oracle:thin:@localhost:1521:orcl
username=root
password=123

 

　　2、定义表所对应的实体类，如下图所示：

　　

　　

package com.model;
// Generated 2017-4-19 10:19:42 by Hibernate Tools 5.2.0.CR1

import java.math.BigDecimal;

import org.apache.ibatis.type.Alias;

/**
 * TestId generated by hbm2java
 */
public class TestId {

    private BigDecimal id;
    private String username;
    private String password;

    public TestId() {
    }

    public TestId(BigDecimal id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }

    public BigDecimal getId() {
        return this.id;
    }

    public void setId(BigDecimal id) {
        this.id = id;
    }

    public String getUsername() {
        return this.username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return this.password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public boolean equals(Object other) {
        if ((this == other))
            return true;
        if ((other == null))
            return false;
        if (!(other instanceof TestId))
            return false;
        TestId castOther = (TestId) other;

        return ((this.getId() == castOther.getId())
                || (this.getId() != null && castOther.getId() != null && this.getId().equals(castOther.getId())))
                && ((this.getUsername() == castOther.getUsername()) || (this.getUsername() != null
                        && castOther.getUsername() != null && this.getUsername().equals(castOther.getUsername())))
                && ((this.getPassword() == castOther.getPassword()) || (this.getPassword() != null
                        && castOther.getPassword() != null && this.getPassword().equals(castOther.getPassword())));
    }

    public int hashCode() {
        int result = 17;

        result = 37 * result + (getId() == null ? 0 : this.getId().hashCode());
        result = 37 * result + (getUsername() == null ? 0 : this.getUsername().hashCode());
        result = 37 * result + (getPassword() == null ? 0 : this.getPassword().hashCode());
        return result;
    }

}

　　3、定义操作test表的sql映射文件userMapper.xml

　　

　　

<?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.dao.UsersMapper">
      <!-- 当数据库表字段和实体类字段不一样时重新定义的方法，在实体类中username改为username1来实验 -->
      <!-- <resultMap type="testId" id="user">
          <result property="username1" column="USERNAME" jdbcType="number" javaType="String"/>
      </resultMap>
      <select id="list1"  resultMap="user">
          select * from test 
      </select>  -->
      <resultMap type="testId" id="users"></resultMap>
      <!-- 查所有表 -->
      <select id="list"  resultType="testId">
          select * from test 
      </select>
      
      <!-- 增 -->
      <insert id="add" parameterType="testId">
          insert into test values(sq_mybatis.nextval,#{username},#{password})
      </insert>
      
      <!-- 删 -->
      <delete id="delete" parameterType="Integer">
          delete test t where t.id=#{id}
      </delete>
      
      <!-- 改 -->
      <update id="update" parameterType="testId">
          update test t set t.username=#{username},t.password=#{password} where t.id=#{id}
      </update>
      
      <!-- 查集合 -->
      <!-- <select id="selectmany" parameterType="Map" resultType="testId" >
          select * from test t where t.username like #{p1} and t.password like #{p2}
      </select> -->
      <select id="selectmany" parameterType="Map" resultMap="users">
          select * from test t where t.username like #{p1} and t.password like #{p2}
      </select>
  </mapper>

　　4、创建一个MybatisUtil的和Junit的类，来进行测试

　　

　　

package com.util;

import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

public class MybatisUtil {
    private static SqlSessionFactory ssf;
    private static SqlSession ss;
    
    public static SqlSession getSqlSession(){
        
        InputStream in = null;
        //Reader reader = null;
        try {
            in= Resources.getResourceAsStream("mybatis.xml");
            //reader = Resources.getResourceAsReader("mbatis.xml");
            
            ssf= new SqlSessionFactoryBuilder().build(in);
            
            ss=ssf.openSession();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return ss;
        
    }
    /*public static void main(String[] args){
        System.out.println(getSqlSession());
    }*/
    
}

package com.util;

import static org.junit.Assert.*;

import java.math.BigDecimal;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.model.TestId;

public class JTest {

    private SqlSession ss;
    
    
    @Before
    public void setUp() throws Exception {
        ss= MybatisUtil.getSqlSession();
    }

    @After
    public void tearDown() throws Exception {
        ss.commit();
        ss.close();
    }

    public void test() {
        List<TestId> list = ss.selectList("com.dao.UsersMapper.list");
        for(TestId t : list ){
            System.out.println(t.getPassword());
        }
    }
    
    
    public void add(){
        TestId ti = new TestId();
        ti.setUsername("hahah");
        ti.setPassword("321");
        int n = ss.insert("com.dao.UsersMapper.add",ti);
        System.out.println(n);
    }
    
    public void delete(){
        int n = ss.delete("com.dao.UsersMapper.delete",61);
        System.out.println(n);
    }
    
    public void update(){
        TestId ti = new TestId();
        ti.setId(new BigDecimal(41));
        ti.setUsername("哈哈哈");
        ti.setPassword("654321");
        int n = ss.update("com.dao.UsersMapper.update",ti);
        System.out.println(n);
    }
    
    @Test
    public void selectmany(){
        Map<String,Object> map = new HashMap<String, Object>();
        map.put("p1", "张%");
        map.put("p2", "2%");
        List<TestId> list=ss.selectList("com.dao.UsersMapper.selectmany",map);
        for(TestId t:list){
            System.out.println(t.getPassword());
        }
    }

}

　　Junit类里面实现了mybatis的增删改查的方法。