mybatis分析前准备

背景

  MyBatis是一个可以自定义SQL、存储过程和高级映射的持久层框架。MyBatis 摒除了大部分的JDBC代码、手工设置参数和结果集重获。MyBatis只使用简单的XML和注解来配置和映射基本数据类型、Map 接口和POJO 到数据库记录。相对Hibernate和Apache OJB等“一站式”ORM解决方案而言，Mybatis 是一种“半自动化”的ORM实现。
  基于自己研究代码的爱好，所以发了一些时间来研读Mybatis源码，学习Mybatis实现方式。

参考文档

• 猿码道：https://www.jianshu.com/nb/5226994
• ashan_li：https://blog.csdn.net/ashan_li/article/details/50337533
• 唯一浩哥 ：http://www.cnblogs.com/V1haoge/p/6603926.html
• 亦山 ：https://blog.csdn.net/luanlouis/article/category/2309433

官方文档

• Mybatis：http://mybatis.org/mybatis-3/zh/

代码准备

• Mapper接口

public interface UserDao {

    public void insert(User user);

    public User findUserById (int userId);

    public List<User> findAllUsers();

    public int updateUser(User user);

    public int deleteUser(User user);

}

• Entity类

public class User {

    private int id;
    private String name;
    private String password;
    private int age;
    private int deleteFlag;

    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 getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public int getDeleteFlag() {
        return deleteFlag;
    }
    public void setDeleteFlag(int deleteFlag) {
        this.deleteFlag = deleteFlag;
    }
}

• Mapper.xml文件

<?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.study.dao.UserDao">

    <resultMap id="userResultMap" type="com.study.entity.User">
        <result column="name" property="name" />
        <result column="id" property="id" />
        <result column="password" property="password" />
        <result column="age" property="age" />
        <result column="deleteFlag" property="deleteFlag" />
    </resultMap>

    <select id="findUserById" resultType="com.study.entity.User">
        select * from study_user where id = #{id}
    </select>


    <select id="findAllUsers" resultType="com.study.entity.User" >
        select * from study_user
    </select>


    <insert id="insert" parameterType="com.study.entity.User">
        insert into study_user (id,name,password,age,deleteFlag) values (#{id},#{name},#{password},#{age},#{deleteFlag})
    </insert>


    <!-- 对应userDao中的updateUser方法 -->
    <update id="updateUser" parameterType="com.study.entity.User">
        update user set name = #{name}, password = #{password}, age = #{age}, deleteFlag = #{deleteFlag}
        where id = #{id}
    </update>

    <!-- 对应userDao中的deleteUser 方法 -->
    <delete id="deleteUser" parameterType="com.study.entity.User">
        delete from user where id = #{id}
    </delete>

</mapper>

• configuration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>

  
  <properties resource="jdbc.properties"></properties>

  
  <settings>
  <setting name="logImpl" value="LOG4J"/>
  </settings>

<environments default="development">
    <environment id="development">
        <transactionManager type="JDBC"/>
        <dataSource type="POOLED">
            <!-- 上面指定了数据库配置文件， 配置文件里面也是对应的这四个属性 -->
            <property name="driver" value="${jdbc.driver}"/>
            <property name="url" value="${jdbc.url}"/>
            <property name="username" value="${jdbc.username}"/>
            <property name="password" value="${jdbc.password}"/>
        </dataSource>
    </environment>
</environments>


<!-- 映射文件，mybatis精髓， 后面才会细讲 -->
<mappers>
    <mapper resource="mapper/UserMapper.xml"/>
</mappers>

</configuration>

• jdbc.properties配置文件

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1/youlangta
jdbc.username=root
jdbc.password=415ilyILY
maxPoolSize=10
minPoolSize=5
autoCommitOnClose=false
checkoutTimeout=1000
acquireRetryAttempts=2

• IUserDaoTest测试类

public class IUserDaoTest {

    @Test
    public void findUserById() {
        SqlSession sqlSession = getSessionFactory().openSession();
        UserDao userMapper = sqlSession.getMapper(UserDao.class);
        User user = userMapper.findUserById(2);
        Assert.assertNotNull("没找到数据", user);
    }

    // Mybatis 通过SqlSessionFactory获取SqlSession, 然后才能通过SqlSession与数据库进行交互
    private static SqlSessionFactory getSessionFactory() {
        SqlSessionFactory sessionFactory = null;
        String resource = "configuration.xml";
        try {
            sessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsReader(resource));
        } catch (IOException e) {
            e.printStackTrace();
        }
        return sessionFactory;
    }
}

• pom文件

<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/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.youlangta.study</groupId>
    <artifactId>mybatisStudy</artifactId>
    <packaging>war</packaging>
    <version>0.0.1-SNAPSHOT</version>
    <name>mybatisStudy Maven Webapp</name>
    <url>http://maven.apache.org</url>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <!-- 使用junit4 -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.1.0</version>
            <!-- 只在编译和测试时运行 -->
            <scope>provided</scope>
        </dependency>
        <!-- 补全项目依赖 -->
        <!-- 1:日志 slf4j是规范/接口 日志实现:log4j,logback,common-logging 这里使用:slf4j + log4j -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>1.7.2</version>
        </dependency>
        <!-- 2:数据库相关依赖 -->
        <dependency>
            <groupId>com.oracle</groupId>
            <artifactId>ojdbc8</artifactId>
            <version>12.2.0.1</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.44</version>
        </dependency>
        <!-- c3p0数据库连接池 -->
        <dependency>
            <groupId>c3p0</groupId>
            <artifactId>c3p0</artifactId>
            <version>0.9.1.2</version>
        </dependency>
        <!-- 3:DAO框架依赖：MyBatis依赖 -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.3.0</version>
        </dependency>
        <!-- MyBatis自身实现的spring整合依赖 -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-spring</artifactId>
            <version>1.2.3</version>
        </dependency>
        <!-- 4:spring依赖 -->
        <!-- 1) spring核心依赖 -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>4.1.7.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>4.1.7.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>4.1.7.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.1.7.RELEASE</version>
        </dependency>
        <!-- 2) spring dao层依赖 -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>4.1.7.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-tx</artifactId>
            <version>4.1.7.RELEASE</version>
        </dependency>
    </dependencies>
    <build>
        <finalName>mybatisStudy</finalName>
    </build>
</project>

• 代码结构

  
  代码.PNG