Mybatis学习_Joker

Mybatis3简介网址

https://mybatis.org/mybatis-3/zh/index.html

Mybaits操作步骤

1.编写工具类

public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;

    static {
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // SqlSession提供了在数据库执行SQL命令所需要的所有方法
    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession();
    }

}

2.在resources文件夹下编写mybatis-config.xml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">

<!--核心配置文件-->
<configuration>
    <!--environment 元素体中包含了事务管理和连接池的配置-->
    <environments default="development">
        <environment id="development">
            <!--事务管理器-->
            <transactionManager type="JDBC"/>
            <!--数据源-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/d107_mybatis?characterEncoding=utf-8"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>

    <!--mappers 元素则包含了一组映射器（mapper），这些映射器的 XML 映射文件包含了 SQL 代码和映射定义信息。-->
    <mappers>
        <mapper resource="org/java/dao/UserMapper.xml" />
    </mappers>
</configuration>

3.编写实体类（字段名要和数据库字段名保持一致）

public class User implements Serializable {
    // 这里的字段名要和数据库的字段名一模一样
    private Integer user_id;
    private String user_name;
    private String user_pwd;

    public User() {
    }

    public User(Integer user_id, String user_name, String user_pwd) {
        this.user_id = user_id;
        this.user_name = user_name;
        this.user_pwd = user_pwd;
    }

    public Integer getUser_id() {
        return user_id;
    }

    public void setUser_id(Integer user_id) {
        this.user_id = user_id;
    }

    public String getUser_name() {
        return user_name;
    }

    public void setUser_name(String user_name) {
        this.user_name = user_name;
    }

    public String getUser_pwd() {
        return user_pwd;
    }

    public void setUser_pwd(String user_pwd) {
        this.user_pwd = user_pwd;
    }

    @Override
    public String toString() {
        return "User[" +
                "user_id=" + user_id +
                ", user_name='" + user_name + '\'' +
                ", user_pwd='" + user_pwd + '\'' +
                ']';
    }
}

4.编写接口

public interface UserMapper {
    /**
     * 查询全部用户
     */
    public List<User> getUserList();

    /**
     * 根据id查询用户
     *
     * @param id 用户Id
     */
    public User getUserById(Integer id);

    /**
     * 使用Map集合根据Id查询信息
     */
    public User getUserById2(Map<String, Object> map);

    /**
     * 根据姓名查询用户
     *
     * @param name 姓名
     */
    public User getUserByName(String name);

    /**
     * 模糊查询
     *
     * @param condition 匹配的条件
     */
    public List<User> fuzzyQuery(String condition);
    
    //mybatis的增删改可以定义Integer|Long|boolean三种返回值类型

    /**
     * 添加一个新用户
     *
     * @param user user
     */
    public Integer addUser(User user);

    /**
     * 根据Map集合添加1个新的用户
     */
    public Integer addUser2(Map<String, Object> map);

    /**
     * 修改用户
     */
    public Integer updateUser(User user);

    /**
     * 根据Map集合修改一个用户信息
     */
    public Integer updateUser2(Map<String, Object> map);

    /**
     * 删除一个用户
     */
    public Integer deleteUser(Integer id);
}

5.编写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">

<!--
namespace:命名空间,指定为接口的全类名
selectUserById：唯一标识
resultType：返回值类型
-->
<mapper namespace="org.java.dao.UserMapper">
    <!--id对应接口中的方法名称-->
    <select id="getUserList" resultType="org.java.pojo.User">
        select * from d107_mybatis.tb_user;
    </select>

    <select id="getUserById" parameterType="Integer" resultType="org.java.pojo.User">
        select * from d107_mybatis.tb_user where user_id = #{id};
    </select>

    <select id="getUserById2" parameterType="map" resultType="org.java.pojo.User">
        select * from d107_mybatis.tb_user where user_id = #{userId} and user_name = #{userName};
    </select>

    <select id="getUserByName" parameterType="String" resultType="org.java.pojo.User">
        select * from d107_mybatis.tb_user where user_name = #{name};
    </select>

    <!--根据用户姓名模糊查询-->
    <select id="fuzzyQuery" parameterType="String" resultType="org.java.pojo.User">
        select * from d107_mybatis.tb_user where user_name like #{condition};
    </select>

    <!--对象中的属性可以直接取出来-->
    <!--增删改需要提交事务-->
    <insert id="addUser" parameterType="org.java.pojo.User">
        insert into d107_mybatis.tb_user values (#{user_id},#{user_name},#{user_pwd});
    </insert>

    <insert id="addUser2" parameterType="map">
        insert into d107_mybatis.tb_user values (#{userId},#{userName},#{password});
    </insert>

    <update id="updateUser" parameterType="org.java.pojo.User">
        update d107_mybatis.tb_user set user_name = #{user_name},user_pwd = #{user_pwd} where user_id = #{user_id};
    </update>

    <!--根据Map集合修改一个用户信息-->
    <update id="updateUser2" parameterType="map">
        update d107_mybatis.tb_user set user_pwd = #{password} where user_id = #{userId};
    </update>

    <delete id="deleteUser" parameterType="Integer">
        delete from d107_mybatis.tb_user where user_id = #{id};
    </delete>
</mapper>

6.编写junit测试类

public class UserDaoTest {
    @Test
    public void test() {
        // 1.获取SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        // 2.执行SQL
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> userList = mapper.getUserList();

        for (User user : userList) {
            System.out.println(user);
        }

        // 3.关闭SqlSession
        sqlSession.close();
    }

    @Test
    public void getUserById() {
        // 获取SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        // 获得接口
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.getUserById(5);
        System.out.println(user);

        // 关闭SqlSession
        sqlSession.close();
    }

    /**
     * 使用Map集合根据Id查询信息
     */
    @Test
    public void getUserById2() {
        // 获取SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        // 获取Mapper
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        Map<String, Object> queryById = new LinkedHashMap<String, Object>();
        queryById.put("userId", 8);
        queryById.put("userName", "令狐冲");

        User user = mapper.getUserById2(queryById);

        System.out.println(user);

        // 关闭SqlSession
        sqlSession.close();
    }

    @Test
    public void getUserByName() {
        // 获取SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        // 获取接口
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.getUserByName("有钱的joker");
        System.out.println(user);

        // 关闭SqlSession
        sqlSession.close();
    }

    /**
     * 根据用户姓名模糊查询
     */
    @Test
    public void fuzzyQuery() {
        // 获取SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        // 获取接口
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> u = mapper.fuzzyQuery("%joker%");

        for (User j : u) {
            System.out.println(j);
        }

        // 关闭SqlSession
        sqlSession.close();
    }

    /**
     * 添加一个新用户
     */
    // 增删改需要提交事务
    @Test
    public void addUser() {
        // 获取SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        Integer count = mapper.addUser(new User(6, "马超", "2001"));
        if (count > 0) {
            System.out.println("----->数据添加成功！");
        } else {
            System.out.println("----->数据添加失败！");
        }

        // 提交事务
        sqlSession.commit();

        // 关闭SqlSession
        sqlSession.close();
    }

    /**
     * 通过Map集合添加一个用户
     */
    @Test
    public void addUser2() {
        // 获取SqlSession
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        // 获取Mapper
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        Map<String, Object> map = new HashMap<String, Object>();
        map.put("userId", null);
        map.put("userName", "赵子龙");
        map.put("password", "20220320");

        mapper.addUser2(map);

        // 提交事务
        sqlSession.commit();

        // 关闭SqlSession
        sqlSession.close();
    }

    /**
     * 修改一个用户
     */
    @Test
    public void updateUser() {
        // 获取SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        // 获取接口
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        mapper.updateUser(new User(8, "令狐冲", "2022"));

        // 提交事务
        sqlSession.commit();

        // 关闭SqlSession
        sqlSession.close();
    }

    /**
     * 根据Map集合修改一个用户
     */
    @Test
    public void updateUser2() {
        // 获取SqlSession
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        // 获取接口
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        Map<String, Object> map = new HashMap<String, Object>();
        map.put("userId", 9);
        map.put("password", "20010910");

        mapper.updateUser2(map);

        // 提交事务
        sqlSession.commit();

        // 关闭SqlSession;
        sqlSession.close();
    }

    /**
     * 删除一个用户
     */
    @Test
    public void deleteUser() {
        // 获取SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        // 获取接口
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        mapper.deleteUser(6);

        // 提交事务
        sqlSession.commit();

        // 关闭SqlSession
        sqlSession.close();

    }
}

pom.xml配置文件

<?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">
    <parent>
        <artifactId>Mybatis-Study</artifactId>
        <groupId>com.joker</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>mybaits-01</artifactId>

    <!--在build中配置resources防止资源导出失败-->
    <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>

mybatis-config.xml文件优化

<?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">

<!--核心配置文件-->
<configuration>
    <!--引入外部配置文件-->
    <properties resource="db.properties" />

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driverClassName}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>

    <!--mappers 元素则包含了一组映射器（mapper），这些映射器的 XML 映射文件包含了 SQL 代码和映射定义信息。-->
    <mappers>
        <mapper resource="org/java/dao/UserMapper.xml" />
    </mappers>
</configuration>

在resources文件夹下创建db.properties文件

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/d107_mybatis?characterEncoding=utf-8
username=root
password=root
initialSize=5
maxActive=10
maxWait=3000

在核心配置文件中引入

<!--方式一-->
<properties resource="db.properties" />

<!--方式二-->
<properties resource="db.properties">
  <property name="username" value="root"/>
  <property name="password" value="root"/>
</properties>

• 可以直接引入外部文件
• 可以在其中增加一些属性配置（username、password）
• 如果两个文件存在同一字段，优先使用外部配置文件（db.properties）

可以给实体类起别名

仅用于 XML 配置，意在降低冗余的全限定类名书写

<!--方式一-->
<typeAliases>
  <typeAlias type="org.java.pojo.User" alias="User" />
</typeAliases>

<!--UserMapper.xml使用方式-->
<select id="getUserList" resultType="User">
  select * from d107_mybatis.tb_user;
</select>

<!--方式二-->
<!--在没有注解的情况下，会使用 Bean 的首字母小写的非限定类名来作为它的别名。 比如 domain.blog.Author 的别名为 author；若有注解，则别名为其注解值。-->
<typeAliases>
  <package name="org.java.pojo"/>
</typeAliases>

<!--UserMapper.xml使用方式-->
<select id="getUserList" resultType="user">
  select * from d107_mybatis.tb_user;
</select>

<!--如果实体类User使用了注解-->
@Alias("hello")
public class User {
    ...
}

<!--则方式二在UserMapper.xml中resultType要改成注解的名字-->
<select id="getUserList" resultType="hello">
  select * from d107_mybatis.tb_user;
</select>

log4j.properties配置文件

#将等级为DEBUG的日志信息输出到console和file这两个目的地，console和file的定义在下面的代码
log4j.rootLogger=DEBUG,console,file

#控制台输出的相关设置
log4j.appender.console = org.apache.log4j.ConsoleAppender
log4j.appender.console.Target = System.out
log4j.appender.console.Threshold=DEBUG
log4j.appender.console.layout = org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern=[%c]-%m%n

#文件输出的相关设置
log4j.appender.file = org.apache.log4j.RollingFileAppender
log4j.appender.file.File=./log/joker.log
log4j.appender.file.MaxFileSize=10mb
log4j.appender.file.Threshold=DEBUG
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=[%p][%d{yy-MM-dd}][%c]%m%n

#日志输出级别
log4j.logger.org.mybatis=DEBUG
log4j.logger.java.sql=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.ResultSet=DEBUG
log4j.logger.java.sql.PreparedStatement=DEBUG

Mybtis实现分页查询

方式1：通过Map集合实现

1.编写UserMapper.java接口

public interface UserMapper {
    /**
     * 分页查询
     */
    public List<User> getUserByLimit(Map<String, Integer> map);
}

2.在UserMapper.xml文件中编写SQL语句

<?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=绑定一个对应的Dao/Mapper接口-->
<mapper namespace="org.java.dao.UserMapper">
    <resultMap id="UserMap" type="User">
        <!--column：数据库中的字段；property：实体类中的属性-->
        <result column="user_id" property="userId"/>
        <result column="user_name" property="userName"/>
        <result column="user_pwd" property="userPwd"/>
    </resultMap>

    <!--分页查询-->
    <select id="getUserByLimit" parameterType="map" resultMap="UserMap">
        select * from d107_mybatis.tb_user limit #{startIndex},#{pageSize};
    </select>
</mapper>

3.测试

public class UserDaoTest {
   /**
     * 分页查询
     */
    @Test
    public void getUserByLimit() {
        // 获取SqlSession
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        // 获取Mapper
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        Map<String, Integer> limitMap = new LinkedHashMap<String, Integer>();
        limitMap.put("startIndex", 2);
        limitMap.put("pageSize", 3);

        List<User> userByLimit = mapper.getUserByLimit(limitMap);
        for (User user : userByLimit) {
            System.out.println(user);
        }

        // 关闭SqlSession
        sqlSession.close();
    }

4.结果

方式2：通过RowBounds实现

1.在UserMapper.java接口中编写方法

public List<User> getUserByRowBounds();

2.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">

<!--namespace=绑定一个对应的Dao/Mapper接口-->
<mapper namespace="org.java.dao.UserMapper">
    <!--根据用户Id查询用户信息-->
    <resultMap id="UserMap" type="User">
        <!--column：数据库中的字段；property：实体类中的属性-->
        <result column="user_id" property="userId"/>
        <result column="user_name" property="userName"/>
        <result column="user_pwd" property="userPwd"/>
    </resultMap>

    <!--通过RowBounds实现分页查询-->
    <select id="getUserByRowBounds" resultMap="UserMap">
        select * from d107_mybatis.tb_user;
    </select>
</mapper>

3.测试

    @Test
    public void getUserByRowBounds() {
        // 获取SqlSession
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        // RowBounds实现
        RowBounds rowBounds = new RowBounds(0, 2);

        // 通过Java代码实现分页
        List<User> rowBoundsList = sqlSession.selectList("org.java.dao.UserMapper.getUserByRowBounds", null, rowBounds);
        for (User user : rowBoundsList) {
            System.out.println(user);
        }

        // 关闭SqlSession
        sqlSession.close();
    }

4.结果