Java进阶知识32 mybatis（ibatis）入门CRUD操作【简单演示，只测DAO层】

本文知识点（目录）：

      1、导读
          1.1、技术概述
          1.2、本文使用的jar包、项目结构图
      2、本文所有代码
          2.1、数据库脚本（oracle.sql）
          2.2、mybatis.xml 核心配置文件
          2.3、MyBatisUtils 工具类（用于连接数据库）
          2.4、Student 实体类
          2.5、Student 实体类的配置文件（StudentMapper.xml）
          2.6、DAO层 （StudentDao）
          2.7、测试类（StudentDaoTest）

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1、导读              

1.1、技术概述

    a.本文使用的是Oracle+mybatis框架，只是演示/测试DAO层（连接数据库，进行数据测试）；

    b.实现了CURD等操作：新增、修改、查询所有、根据id查询、删除、批量删除

    c.本项目的使用环境：MyEclipse10.7 + JDK1.8 + Oracle11g + mybatis3.1.1

1.2、本文使用的jar包、项目结构图

2、本文所有代码     

2.1、数据库脚本（oracle.sql）

-- 创建表
create table student(
    id number(6) primary key,
    name varchar2(20),
    sex number(1),
    age number(3),
    telphone varchar2(16)
);

-- 创建序列
create sequence student_seq
minvalue 1    --最小值
maxvalue 99999    -- 最大值
increment by 1    --从1开始计数
start with 1    --每次加1
nocycle        --一直累加，不循环
nocache;    --不建缓冲区。

create or replace trigger student_tg
  before insert on student for each row 
    begin
      select student_seq.Nextval into:new.id from dual;
  end;

-- 插入数据
insert into student(name,sex,age,telphone) values('zhangsan',1,23,'18795901366');

2.2、mybatis.xml 核心配置文件

<?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="oracle.jdbc.driver.OracleDriver" />
                <property name="url" value="jdbc:oracle:thin:@localhost:1521:shoreid" />
                <property name="username" value="zhangsan" />
                <property name="password" value="123456" />
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="com/shore/entity/StudentMapper.xml"/>
    </mappers>
</configuration>

2.3、MyBatisUtils 工具类（用于连接数据库）

package com.shore.utils;

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;

/**
 * @author DSHORE/2020-3-11
 *
 */
public class MyBatisUtils {
    private static ThreadLocal<SqlSession> threadLocal = new ThreadLocal<SqlSession>();
    private static SqlSessionFactory sqlSessionFactory;
    
    static{
        try {
            //1、读取配置
            Reader reader = Resources.getResourceAsReader("mybatis.xml");
            //2、创建SqlSessionFactory
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
        } catch (Exception e) {
            e.fillInStackTrace();
            throw new RuntimeException(e);
        }
    }
    
    private MyBatisUtils() { }
    
    //获取SqlSession
    public static SqlSession getSqlSession(){
        SqlSession sqlSession = threadLocal.get();
        if (sqlSession == null) {//如果上面获取不到SQLSession，将通过下面的方式来获取
            sqlSession = sqlSessionFactory.openSession();
        }
        return sqlSession;
    }
    
    //关闭SqlSession
    public static void closeSqlSession() {
        SqlSession sqlSession = threadLocal.get();
        if (sqlSession != null) {
            sqlSession.close();
            threadLocal.remove();
        }
    }
}

2.4、Student 实体类

package com.shore.entity;

/**
 * @author DSHORE/2020-3-11
 *
 */
public class Student {
    private Integer id;
    private String name;
    private Integer sex;
    private Integer age;
    private String telphone;
    
    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getSex() {
        return sex;
    }

    public void setSex(Integer sex) {
        this.sex = sex;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getTelphone() {
        return telphone;
    }

    public void setTelphone(String telphone) {
        this.telphone = telphone;
    }

    @Override
    public String toString() {
        return "Student [id=" + id + ", name=" + name + ", sex=" + sex
                + ", age=" + age + ", telphone=" + telphone + "]";
    }
}

2.5、Student 实体类的配置文件（StudentMapper.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="student">
    <!--=======================查询============================= -->
    <!-- 1、查询所有 -->
    <select id="selectAll" resultType="com.shore.entity.Student">
        select * from student
    </select>
    
    <!-- 2、根据id查询 -->
    <select id="findById" parameterType="int" resultType="com.shore.entity.Student">
        select * from student where id=#{id}
    </select>

    <!-- 3、动态条件查询 -->
    <select id="dynamicSelect" parameterType="map" resultType="com.shore.entity.Student">
        select * from student
        <where>
            <if test="name != null">
                and name = #{name}
            </if>
            <if test="telphone != null">
                and telphone = #{telphone}
            </if>
        </where>
    </select>

    <!--=======================4、新增============================= -->
    <insert id="dynamicInsert" parameterType="com.shore.entity.Student">
        insert into student(name,sex,age,telphone)
         values(#{name},#{sex},#{age},#{telphone})
    </insert>

    <!--=======================5、更新============================= -->
    <update id="dynamicUpdate" parameterType="com.shore.entity.Student">
        update student
        set name=#{name},
        sex=#{sex},
        age=#{age},
        telphone=#{telphone}
        where id=#{id}
    </update>

    <!--=======================6、删除============================= -->
    <delete id="deleteById" parameterType="int">
        delete from student where id=#{id}
    </delete>
    
    <!--=======================7、批量删除============================= -->
    <delete id="batchDeleteById">
        delete from student where id in 
        <foreach item="ids" collection="list" open="(" separator="," close=")">
            #{ids}
        </foreach>
    </delete>
</mapper>

2.6、DAO层 （StudentDao）

为了方便，此处不写接口，我直接写实现类

package com.shore.dao;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.ibatis.session.SqlSession;

import com.shore.entity.Student;
import com.shore.utils.MyBatisUtils;

/**
 * @author DSHORE/2020-3-11
 *
 */
public class StudentDao {
    // 1、查询全部
    public List<Student> listAll() {
        List<Student> bosses = new ArrayList<Student>();
        SqlSession sqlSession = MyBatisUtils.getSqlSession();
        try {
            bosses = sqlSession.selectList("student.selectAll");
        } catch (Exception e) {
            // sqlSession.rollback(); //事务回滚
            System.out.println("error:" + e.getMessage());//获取异常信息，打印到控台
        } finally {
            // sqlSession.commit(); //查询操作不用提交、不用回滚
            MyBatisUtils.closeSqlSession();//关闭SqlSession
        }
        return bosses;
    }
    
    // 2、根据id查询
    public Student findById(int id) {
        Student student = null;
        SqlSession sqlSession = MyBatisUtils.getSqlSession();
        try {
            List<Student> students = sqlSession.selectList("student.findById", id);
            if (students != null && students.size() > 0) {
                student = students.get(0);
            }
        } catch (Exception e) {
            System.out.println("error:" + e.getMessage());//获取异常信息，打印到控台
        } finally {
            MyBatisUtils.closeSqlSession();//关闭SqlSession
        }
        return student;
    }
    
    // 3、动态条件查询
    public List<Student> dynamicSelect(String name, String telphone) {
        List<Student> students = new ArrayList<Student>();
        SqlSession sqlSession = MyBatisUtils.getSqlSession();
        try {
            Map<String, String> map = new HashMap<String, String>();
            map.put("name", name);
            map.put("telphone", telphone);
            students = sqlSession.selectList("student.dynamicSelect", map);
        } catch (Exception e) {
            System.out.println("error:" + e.getMessage());
        } finally {
            MyBatisUtils.closeSqlSession();
        }
        return students;
    }
    
    // 4、动态插入
    public int dynamicInsert(Student student) {
        SqlSession sqlSession = MyBatisUtils.getSqlSession();
        try {
            return sqlSession.insert("student.dynamicInsert", student);
        } catch (Exception e) {
            sqlSession.rollback();//如果出现异常，则事务回滚
        } finally {
            sqlSession.commit();//提交事务
            MyBatisUtils.closeSqlSession();//关闭SqlSession
        }
        return 0;
    }
    
    // 5、动态更新
    public int dynamicUpdate(Student student) {
        SqlSession sqlSession = MyBatisUtils.getSqlSession();
        try {
            return sqlSession.update("student.dynamicUpdate", student);
        } catch (Exception e) {
            sqlSession.rollback();
        } finally {
            sqlSession.commit();
            MyBatisUtils.closeSqlSession();
        }
        return 0;
    }
    
    // 6、删除(根据id删除)
    public int deleteByInt(int id) {
        SqlSession sqlSession = MyBatisUtils.getSqlSession();
        try {
            return sqlSession.delete("student.deleteById", id);
        } catch (Exception e) {
            sqlSession.rollback();
        } finally {
            sqlSession.commit();
            MyBatisUtils.closeSqlSession();
        }
        return 0;
    }
    
    // 7、批量删除
    public int batchDeleteById(List<Integer> ids) {
        SqlSession sqlSession = MyBatisUtils.getSqlSession();
        try {
            return sqlSession.delete("student.batchDeleteById", ids);
        } catch (Exception e) {
            sqlSession.rollback();
            System.out.println("error:"+e.getMessage());
        } finally {
            sqlSession.commit();
            MyBatisUtils.closeSqlSession();
        }
        return 0;
    }
}

2.7、测试类（StudentDaoTest）

package com.shore.test;

import java.util.ArrayList;
import java.util.List;

import org.junit.Test;

import com.shore.dao.StudentDao;
import com.shore.entity.Student;

/**
 * @author DSHORE/2020-3-11
 *
 */
public class StudentDaoTest {
    StudentDao studentDao = new StudentDao();
    
    @Test // 1、查询全部
    public void testListAll() {
        List<Student> students = studentDao.listAll();
        if (students == null) {
            System.out.println("students is null。");
        } else {
            //返回值：Student [id=1, name=zhangsan, sex=0, age=26, telphone=12345678900]
            System.out.println(students.get(0));
        }
    }
    
    @Test // 2、根据id查询
    public void testFindById() {
        Student student = studentDao.findById(1);
        //返回值：Student [id=1, name=zhangsan, sex=0, age=26, telphone=12345678900]
        System.out.println(student);
    }
    
    @Test // 3、动态条件查询
    public void testDynamicSelect() {
        List<Student> students = studentDao.dynamicSelect(null, "18795901366");
        List<Student> students2 = studentDao.dynamicSelect("zhangsan","12345678900");
        System.out.println(students.size());//返回值：1
        //返回值：Student [id=1, name=zhangsan, sex=0, age=26, telphone=12345678900]
        System.out.println(students2.get(0));
    }
    
    // 4、动态插入
    @Test
    public void testDynamicInsert() {
        Student student = new Student();
        student.setName("王五");
        student.setSex(1);//0代表男，1代表女
        student.setAge(26);
        student.setTelphone("13859501266");
        System.out.println(studentDao.dynamicInsert(student));//返回值：1     说明插入数据成功
    }
    
    // 5、动态更新
        @Test
    public void testDynamicUpdate() {
        Student student = new Student();
        student.setId(7);
        student.setName("李四");
        student.setSex(0);
        student.setAge(23);
        student.setTelphone("18795901366");
        System.out.println(studentDao.dynamicUpdate(student));//返回值：1     说明更新数据成功
    }
    
    // 6、删除
    @Test
    public void testDelete() {
        System.out.println(studentDao.deleteByInt(3));//返回值：1    说明删除数据成功
    }
    
    // 7、批量删除
    @Test
    public void testBatchDelete() {
        List<Integer> ids = new ArrayList<Integer>();
        ids.add(4);
        ids.add(5);
        ids.add(6);
        System.out.println(studentDao.batchDeleteById(ids));//返回值：3    说明批量删除数据成功
    }
}

到此已完结！有任何问题，可留言。

mybatis单向一对一关联映射：https://www.cnblogs.com/dshore123/p/12489304.html
mybatis单向一对多关联映射：https://www.cnblogs.com/dshore123/p/12493450.html
mybatis单向多对多关联映射：https://www.cnblogs.com/dshore123/p/12526016.html

原创作者：DSHORE

作者主页：http://www.cnblogs.com/dshore123/

原文出自：https://www.cnblogs.com/dshore123/p/12463550.html

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