使用mybatis查询数据库示例练习3

在示例练习2中，我们已经新建了maven空工程，并且新建了一个moudle模块，也编写了代码，但是其中在包dao下，我们新建的代码UserDao与Mapper配合使用，不符合规范。下面是经过优化的代码。

 

总项目的pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.shrimpking</groupId>
    <artifactId>mybatistest02</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>mybatis-01</module>
        <module>mybatis-01-self</module>
        <module>mybatis-02</module>
        <module>mybatis-03</module>
        <module>mybatis-04</module>
        <module>mybatis-05</module>
        <module>mybatis-05</module>
        <module>mybatis-06</module>
        <module>mybatis-07</module>
        <module>mybatis-08</module>
        <module>mybatis-09-blog</module>
    </modules>

    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>

        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
    </dependencies>

    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>
</project>

项目具体情况截图

 下面依次是各文件代码：

mybatis-config.xml

<?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/test?useUnicode=true&useSSL=false&characterEncoding=utf-8&serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="mysql123"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="com/shrimpking/mapper/UserMapper.xml"/>
    </mappers>
</configuration>

MyBatisUtils.java

package com.shrimpking.utils;

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 java.io.Reader;

/**
 * @author user1
 */
public class MybatisUtils
{

    private static SqlSessionFactory sqlSessionFactory;

    static {
        try
        {
            String resource = "mybatis-config.xml";
            Reader reader = Resources.getResourceAsReader(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
            reader.close();
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }

    public static SqlSession getSqlSession()
    {
        return sqlSessionFactory.openSession();
    }
}

User.java

package com.shrimpking.pojo;

/**
 * @author user1
 */
public class User
{
    private int id;
    private String name;
    private String pwd;

    public User()
    {
    }

    public User(int id, String name, String pwd)
    {
        this.id = id;
        this.name = name;
        this.pwd = pwd;
    }

    public int getId()
    {
        return id;
    }

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

    public String getName()
    {
        return name;
    }

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

    public String getPwd()
    {
        return pwd;
    }

    public void setPwd(String pwd)
    {
        this.pwd = pwd;
    }

    @Override
    public String toString()
    {
        return "User{" + "id=" + id + ", name='" + name + '\'' + ", pwd='" + pwd + '\'' + '}';
    }
}

UserMapper.java

package com.shrimpking.mapper;

import com.shrimpking.pojo.User;

import java.util.List;

/**
 * @author user1
 */
public interface UserMapper
{
    List<User> getUserList();
}

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.shrimpking.mapper.UserMapper">
    <select id="getUserList" resultType="com.shrimpking.pojo.User">
        select * from user;
    </select>
</mapper>

数据库：

create table user(
	id int(20) not null,
	name varchar(30) default null,
	pwd varchar(30) default null,
	primary key(id)
);

insert into user values(1,'张三','123456');
insert into user values(2,'李四','123456');
insert into user values(3,'王五','123456');

DemoTest.java

package com.shrimpking.dao;

import com.shrimpking.mapper.UserMapper;
import com.shrimpking.pojo.User;
import com.shrimpking.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class DemoTest
{
    @Test
    public void test()
    {
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = mapper.getUserList();
        for (User user : userList)
        {
            System.out.println(user);
        }
        sqlSession.close();
    }
}