使用MyBatis编写Dao的两种语法

原文链接：

在mybatis中，我们有两种dao的写法，一种叫传统dao写法，一种叫mapper代理接口。下面看看如何实现。

1 传统dao写法

1.1 编写customerdao接口

package com.yiidian.dao;
import com.yiidian.domain.customer;
import java.util.list;
/**
 * dao接口
 *一点教程网 - www.yiidian.com
 */
public interface customerdao {

    /**
     * 查询所有用户
     */
    public list<customer> findall();

    /**
     * 添加
     */
    public void save(customer customer);

    /**
     * 修改
     */
    public void update(customer customer);

    /**
     * 查询一个
     */
    public customer findbyid(integer id);

    /**
     * 条件查询
     */
    public list<customer> findbyname(string name);

    /**
     * 删除
     */
    public void delete(integer id);
}

1.2 编写customerdao实现类

package com.yiidian.dao.impl;

import com.yiidian.dao.customerdao;
import com.yiidian.domain.customer;
import com.yiidian.utils.mybatisutils;
import org.apache.ibatis.session.sqlsession;

import java.util.list;

/**
 * dao实现类
 */
public class customerdaoimpl implements customerdao{
    @override
    public list<customer> findall() {
        sqlsession sqlsession = null;
        try {
            sqlsession = mybatisutils.getsession();
            return sqlsession.selectlist("com.yiidian.dao.customerdao.findall");
        } catch (exception e) {
            e.printstacktrace();
        } finally{
            sqlsession.close();
        }
        return null;
    }

    @override
    public void save(customer customer) {
        sqlsession sqlsession = null;
        try {
            sqlsession = mybatisutils.getsession();
            sqlsession.insert("com.yiidian.dao.customerdao.save", customer);
            sqlsession.commit();
        } catch (exception e) {
            e.printstacktrace();
            sqlsession.rollback();
        } finally{
            sqlsession.close();
        }
    }

    @override
    public void update(customer customer) {
        sqlsession sqlsession = null;
        try {
            sqlsession = mybatisutils.getsession();
            sqlsession.update("com.yiidian.dao.customerdao.update", customer);
            sqlsession.commit();
        } catch (exception e) {
            e.printstacktrace();
            sqlsession.rollback();
        } finally{
            sqlsession.close();
        }
    }

    @override
    public customer findbyid(integer id) {
        sqlsession sqlsession = null;
        try {
            sqlsession = mybatisutils.getsession();
            return sqlsession.selectone("com.yiidian.dao.customerdao.findbyid",id);
        } catch (exception e) {
            e.printstacktrace();
        } finally{
            sqlsession.close();
        }
        return null;
    }

    @override
    public list<customer> findbyname(string name) {
        sqlsession sqlsession = null;
        try {
            sqlsession = mybatisutils.getsession();
            return sqlsession.selectlist("com.yiidian.dao.customerdao.findbyname",name);
        } catch (exception e) {
            e.printstacktrace();
        } finally{
            sqlsession.close();
        }
        return null;
    }

    @override
    public void delete(integer id) {
        sqlsession sqlsession = null;
        try {
            sqlsession = mybatisutils.getsession();
            sqlsession.delete("com.yiidian.dao.customerdao.delete", id);
            sqlsession.commit();
        } catch (exception e) {
            e.printstacktrace();
            sqlsession.rollback();
        } finally{
            sqlsession.close();
        }
    }
}

传统方式的重点在于dao实现类，在dao实现类中，手动调用sqlsession提供的方法直接执行映射文件的sql语句。

1.3 编写customerdao.xml映射

<?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">
<!--
   namespace: 用于指定该映射文件需要映射的dao接口
-->
<mapper namespace="com.yiidian.dao.customerdao">

    <!--查询所有-->
    <select id="findall" resulttype="com.yiidian.domain.customer">
        select * from t_customer
    </select>

    <!--1.添加方法-->
    <insert id="save" parametertype="com.yiidian.domain.customer">
        insert into t_customer(name,gender,telephone) values(#{name},#{gender},#{telephone})
    </insert>

    <!--2.修改方法-->
    <update id="update" parametertype="com.yiidian.domain.customer">
        update t_customer set
        name = #{name},
        gender = #{gender},
        telephone = #{telephone}
        where id = #{id}
    </update>

    <!--查询一个-->
    <select id="findbyid" parametertype="integer" resulttype="com.yiidian.domain.customer">
        select * from t_customer where id = #{id}
    </select>

    <!--条件查询-->
    <select id="findbyname" parametertype="string" resulttype="com.yiidian.domain.customer">
        select * from t_customer where name like #{name}
    </select>

    <!--删除-->
    <delete id="delete" parametertype="integer">
        delete from t_customer where id = #{id}
    </delete>
</mapper>

1.4 编写测试类

package com.yiidian.mybatis;

import com.yiidian.dao.customerdao;
import com.yiidian.dao.impl.customerdaoimpl;
import com.yiidian.domain.customer;
import com.yiidian.utils.mybatisutils;
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 org.junit.test;

import java.io.ioexception;
import java.io.inputstream;
import java.util.list;

/**
 * mybatis测试类 - 传统dao写法
 * 一点教程网 - www.yiidian.com
 */
public class testcustomerdao {

    /**
     * 添加
     */
    @test
    public void testsave(){
        //1.获取sqlsession对象
        sqlsession session = mybatisutils.getsession();

        //2.创建传统dao实现类对象
        customerdao customerdao = new customerdaoimpl();

        //3.调用save方法
        customer customer = new customer();
        customer.setname("小苍");
        customer.setgender("女");
        customer.settelephone("15755556666");
        customerdao.save(customer);


        //4.关闭连接
        session.close();
    }

    /**
     * 修改
     */
    @test
    public void testupdate(){
        //1.获取sqlsession对象
        sqlsession session = mybatisutils.getsession();

        //2.创建传统dao实现类对象
        customerdao customerdao = new customerdaoimpl();

        //3.调用update方法
        customer customer = new customer();
        customer.setid(5);
        customer.setname("小泽");
        customer.setgender("女");
        customer.settelephone("15755556666");
        customerdao.update(customer);

        session.commit();

        //4.关闭连接
        session.close();
    }

    /**
     * 查询所有
     */
    @test
    public void testfindall(){
        //1.获取sqlsession对象
        sqlsession session = mybatisutils.getsession();

        //2.创建传统dao实现类对象
        customerdao customerdao = new customerdaoimpl();

        //3.调用findall方法
        list<customer> list = customerdao.findall();

        for(customer cust:list){
            system.out.println(cust);
        }

        //4.关闭连接
        session.close();
    }

    /**
     * 查询一个
     */
    @test
    public void testfindbyid(){
        //1.获取sqlsession对象
        sqlsession session = mybatisutils.getsession();

        //2.创建传统dao实现类对象
        customerdao customerdao = new customerdaoimpl();

        //3.调用findbyid方法
        customer customer = customerdao.findbyid(3);

        system.out.println(customer);

        //4.关闭连接
        session.close();
    }

    /**
     * 条件查询
     */
    @test
    public void testfindbyname(){
        //1.获取sqlsession对象
        sqlsession session = mybatisutils.getsession();

        //2.创建传统dao实现类对象
        customerdao customerdao = new customerdaoimpl();

        //3.调用findbyname方法
        list<customer> list = customerdao.findbyname("%小%");

        for(customer cust:list){
            system.out.println(cust);
        }

        //4.关闭连接
        session.close();
    }

    /**
     * 删除
     */
    @test
    public void testdelete(){
        //1.获取sqlsession对象
        sqlsession session = mybatisutils.getsession();

        //2.创建传统dao实现类对象
        customerdao customerdao = new customerdaoimpl();

        //3.调用findbyname方法
        customerdao.delete(5);

        // 提交事务
        session.commit();

        //4.关闭连接
        session.close();
    }
}

2 mapper代理接口

2.1 编写customerdao接口

package com.yiidian.dao;
import com.yiidian.domain.customer;
import java.util.list;
/**
 * dao接口
 *一点教程网 - www.yiidian.com
 */
public interface customerdao {

    /**
     * 查询所有用户
     */
    public list<customer> findall();

    /**
     * 添加
     */
    public void save(customer customer);

    /**
     * 修改
     */
    public void update(customer customer);

    /**
     * 查询一个
     */
    public customer findbyid(integer id);

    /**
     * 条件查询
     */
    public list<customer> findbyname(string name);

    /**
     * 删除
     */
    public void delete(integer id);
}

2.2 编写customerdao.xml映射

<?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">
<!--
   namespace: 用于指定该映射文件需要映射的dao接口
-->
<mapper namespace="com.yiidian.dao.customerdao">

    <!--查询所有-->
    <select id="findall" resulttype="com.yiidian.domain.customer">
        select * from t_customer
    </select>

    <!--1.添加方法-->
    <insert id="save" parametertype="com.yiidian.domain.customer">
        insert into t_customer(name,gender,telephone) values(#{name},#{gender},#{telephone})
    </insert>

    <!--2.修改方法-->
    <update id="update" parametertype="com.yiidian.domain.customer">
        update t_customer set
        name = #{name},
        gender = #{gender},
        telephone = #{telephone}
        where id = #{id}
    </update>

    <!--查询一个-->
    <select id="findbyid" parametertype="integer" resulttype="com.yiidian.domain.customer">
        select * from t_customer where id = #{id}
    </select>

    <!--条件查询-->
    <select id="findbyname" parametertype="string" resulttype="com.yiidian.domain.customer">
        select * from t_customer where name like #{name}
    </select>

    <!--删除-->
    <delete id="delete" parametertype="integer">
        delete from t_customer where id = #{id}
    </delete>
</mapper>

2.3 编写测试类

package com.yiidian.mybatis;

import com.yiidian.dao.customerdao;
import com.yiidian.dao.impl.customerdaoimpl;
import com.yiidian.domain.customer;
import com.yiidian.utils.mybatisutils;
import org.apache.ibatis.session.sqlsession;
import org.junit.test;

import java.util.list;

/**
 * mybatis测试类 - mapper代理接口
 * 一点教程网 - www.yiidian.com
 */
public class testcustomerdao2 {

    /**
     * 添加
     */
    @test
    public void testsave(){
        //1.获取sqlsession对象
        sqlsession session = mybatisutils.getsession();

        //2.生成dao代理对象
        customerdao customerdao = session.getmapper(customerdao.class);

        //3.调用save方法
        customer customer = new customer();
        customer.setname("小苍");
        customer.setgender("女");
        customer.settelephone("15755556666");
        customerdao.save(customer);


        //4.关闭连接
        session.close();
    }

    /**
     * 修改
     */
    @test
    public void testupdate(){
        //1.获取sqlsession对象
        sqlsession session = mybatisutils.getsession();

        //2.生成dao代理对象
        customerdao customerdao = session.getmapper(customerdao.class);

        //3.调用update方法
        customer customer = new customer();
        customer.setid(5);
        customer.setname("小泽");
        customer.setgender("女");
        customer.settelephone("15755556666");
        customerdao.update(customer);

        session.commit();

        //4.关闭连接
        session.close();
    }

    /**
     * 查询所有
     */
    @test
    public void testfindall(){
        //1.获取sqlsession对象
        sqlsession session = mybatisutils.getsession();

        //2.生成dao代理对象
        customerdao customerdao = session.getmapper(customerdao.class);

        //3.调用findall方法
        list<customer> list = customerdao.findall();

        for(customer cust:list){
            system.out.println(cust);
        }

        //4.关闭连接
        session.close();
    }

    /**
     * 查询一个
     */
    @test
    public void testfindbyid(){
        //1.获取sqlsession对象
        sqlsession session = mybatisutils.getsession();

        //2.生成dao代理对象
        customerdao customerdao = session.getmapper(customerdao.class);

        //3.调用findbyid方法
        customer customer = customerdao.findbyid(5);

        system.out.println(customer);

        //4.关闭连接
        session.close();
    }

    /**
     * 条件查询
     */
    @test
    public void testfindbyname(){
        //1.获取sqlsession对象
        sqlsession session = mybatisutils.getsession();

        //2.生成dao代理对象
        customerdao customerdao = session.getmapper(customerdao.class);

        //3.调用findbyname方法
        list<customer> list = customerdao.findbyname("%小%");

        for(customer cust:list){
            system.out.println(cust);
        }

        //4.关闭连接
        session.close();
    }

    /**
     * 删除
     */
    @test
    public void testdelete(){
        //1.获取sqlsession对象
        sqlsession session = mybatisutils.getsession();

        //2.生成dao代理对象
        customerdao customerdao = session.getmapper(customerdao.class);

        //3.调用findbyname方法
        customerdao.delete(5);

        // 提交事务
        session.commit();

        //4.关闭连接
        session.close();
    }
}

源码下载：https://pan.baidu.com/s/1zsm5cau026zff3wzea-afq

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