mybatis的入门指南，mybatis入门指南

mybatis的入门指南

在mysql建表及插入数据

SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
--  Table structure for `users`
-- ----------------------------
DROP TABLE IF EXISTS `users`;
CREATE TABLE `users` (
  `username` varchar(45) NOT NULL,
  `password` varchar(45) NOT NULL,
  `enabled` tinyint(4) NOT NULL DEFAULT '1',
  PRIMARY KEY (`username`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `users`
-- ----------------------------
BEGIN;
INSERT INTO `users` VALUES ('alex', '123456', '1'), ('mkyong', '123456', '1'), ('user', '654321', '1');
COMMIT;

SET FOREIGN_KEY_CHECKS = 1;

在eclipse建立一个普通的maven java工程

选择maven工程，方便管理

选择普通的java工程

下一步，输入相关的名字，最终的项目结构如下：

名字不一样，结构是一样的。

添加项目的jar依赖

<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.example</groupId>
    <artifactId>mybatis01</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>mybatis01</name>
    <url>http://maven.apache.org</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>3.8.1</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.2.1</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>6.0.6</version>
        </dependency>
    </dependencies>
</project>

使用mybatis查询数据

添加mybatis配置文件conf.xml

内容如下：

<?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>
    <typeAliases>
        <typeAlias type="com.example.mybatis01.domain.User" alias="user" />
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/test?characterEncoding=utf8&amp;useSSL=true" />
                <property name="username" value="root" />
                <property name="password" value="123456@#" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <!-- 注册userMapper.xml文件， userMapper.xml位于com.example.mybatis01.mapping这个包下，所以resource写成com/example/mybatis01/mapping/userMapper.xml -->
        <mapper resource="com/example/mybatis01/mapping/userMapper.xml" />
    </mappers>

</configuration>

typeAlias节点给实体类取一个别名，方便后面引用，environment节点是数据库连接的相关信息，mapper节点指明映射文件的地址，上面的文件内容如下：
User.java

package com.example.mybatis01.domain;

public class User {
    private String username;
    private String password;
    private boolean enabled;
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public boolean isEnabled() {
        return enabled;
    }
    public void setEnabled(boolean enabled) {
        this.enabled = enabled;
    }
    @Override
    public String toString() {
        return "User [username=" + username + ", password=" + password + ", enabled=" + enabled + "]";
    }

}

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.example.mybatis01.mapping.UserMapper">
    <insert id="insert" parameterType="user">
        insert into users(username,
        password,enabled) values(#{username}, #{password},#{enabled})
    </insert>
    <select id="selectUser" parameterType="String" resultType="user">
        SELECT * FROM users WHERE username = #{username}
    </select>
    <select id="selectAll" resultType="user">
        SELECT * FROM users
    </select>
</mapper>

然后写个App.java main类，测试使用mybatis访问到的数据，

package com.example.mybatis01;

import java.io.InputStream;

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

import com.example.mybatis01.domain.User;

/**
 * Hello world!
 *
 */
public class App {
    public static void main(String[] args) {
        //mybatis的配置文件
        String resource = "conf.xml";
        //使用类加载器加载mybatis的配置文件（它也加载关联的映射文件）
        InputStream is = App.class.getClassLoader().getResourceAsStream(resource);
        //构建sqlSession的工厂
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);
        //创建能执行映射文件中sql的sqlSession
        SqlSession session = sessionFactory.openSession();
        /**
         * 映射sql的标识字符串，
         * com.example.mybatis01.mapping.UserMapper是userMapper.xml文件中mapper标签的namespace属性的值，
         * selectUser是select标签的id属性值，通过select标签的id属性值就可以找到要执行的SQL
         */
        String statement = "com.example.mybatis01.mapping.UserMapper.selectUser";//映射sql的标识字符串
        //执行查询返回一个唯一user对象的sql
        User user = session.selectOne(statement, "alex");
        System.out.println(user);

        System.out.println(session.selectList("com.example.mybatis01.mapping.UserMapper.selectAll"));

    }
}

最后项目的结构如下：

运行main方法，打印出结果如下：

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