SSM框架学习笔记day4---Mybatis核心组件

2024-03-28 19:29:28

3.1持久层和mybatis

关键词：
不屏蔽SQL
映射机制灵活
提供使用Mapper的接口编程
环境：

3.2Mybatis核心组件

SqlSessionFactoryBuilder（构造器）：根据配置或者代码生成SqlSessionFactory,采用分步构建的builder模式
SqlSessionFactory(工厂接口):使用工厂模式生成SqlSession
SqlSession(会话)：即可以发送SQL执行返回结果，也可以获取Mapper的接口。
SqlMapper:由一个java接口和XML文件构成，需要对应sql规则

3.2SQLSessionFactory(工厂接口)

使用XML构建SQLSessionFactory

config

<?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><!--别名-->
        <typeAlias alias="role" type="bean.Role"/>
    </typeAliases>
    <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/ssm_mybatis"/>
                <property name="username" value="root"/>
                <property name="password" value="wang"/>
            </dataSource>
        </environment>
    </environments>
    <!--映射文件-->
    <mappers>
         <mapper resource="bean/Mapper/RoleMapper.xml"/>
    </mappers>
</configuration>

使用代码创建SqlSessionFactory的方法

package util;

import bean.Role;
import org.apache.ibatis.datasource.pooled.PooledDataSource;
import org.apache.ibatis.mapping.Environment;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.apache.ibatis.transaction.TransactionFactory;
import org.apache.ibatis.transaction.jdbc.JdbcTransactionFactory;


public class DBUtil {
    private PooledDataSource dataSource = null;
    private TransactionFactory transactionFactory = null;
    private Environment environment = null;
    private Configuration configuration = null;
    private SqlSessionFactory sqlSessionFactory = null;

    public SqlSessionFactory createCon(){
        //数据库连接池信息
        dataSource = new PooledDataSource();
        dataSource.setDriver("com.mysql.jdbc.Driver");
        dataSource.setUrl("jdbc:mysql://localhost:3306/ssm_mybatis");
        dataSource.setUsername("root");
        dataSource.setPassword("wang");

        //mybatis的JDBC事务方式
        transactionFactory = new JdbcTransactionFactory();
        environment = new Environment("development",transactionFactory,dataSource);

        //创建Configuration对象
        configuration = new Configuration(environment);
        //注册别名
        configuration.getTypeAliasRegistry().registerAlias("role", Role.class);
        //加入映射器
        configuration.addMapper(RoleMapper.class);
        //使用SqlSessionFactoryBuilder构建SqlSessionFactory
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);

        return sqlSessionFactory;
    }
}

SqlSession

获取Mapper接口；
发送sql；
控制数据库事务；
DefaultSqlSession:单线程
SqlSessionManage:多线程

创建SqlSession

    private SqlSession sqlSession= null;

    //事务控制伪代码
    public void actionController(){
        
        try {
            //打开session会话
            sqlSession = createCon().openSession();
            //做一些处理
            //提交
            sqlSession.commit();
        }catch (Exception e){
            sqlSession.rollback();//存在异常回滚
        }finally {
            //确保资源顺利关闭
            if (sqlSession!=null){
                sqlSession.close();
            }
        }
    }

映射器

可配置的内容：
描述映射规则
提供sql语句，并配置参数类型，返回类型，缓存刷新等信息
配置缓存
提供动态sql

Role类//引用了lombok1.18.0

package bean;


import lombok.Getter;
import lombok.Setter;

@Setter
@Getter
public class Role {
    private Long id;
    private String roleName;
    private String note;
}

映射上面的类
接口：

package Mapper;

import bean.Role;

public interface RoleMapper {
    public Role getRole();
}

mapper：

<?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="Mapper.RoleMapper">
    <select id="getRole" parameterType="long" resultType="role">
        select id,role_name as roleName,note from role where id = #{id}
    </select>
</mapper>

配置文件中：

    <!--映射文件-->
    <mappers>
         <mapper resource="bean/Mapper/RoleMapper.xml"/>
    </mappers>

即为注册该XML文件，用XML方式创建映射器

实例：
目录

pom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">
    <modelVersion>4.0.0</modelVersion>

    <groupId>SSM</groupId>
    <artifactId>SSM</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.16.20</version>
        </dependency>

        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.1</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>

        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.16</version>
        </dependency>
    </dependencies>
    <build>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.xml</include>
                </includes>
            </resource>
        </resources>
    </build>
</project>

RoleMapper:

实现增删改查

RoleMapper:

<?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="Mapper.RoleMapper">

    <insert id="insertRole" parameterType="role">
        insert into t_role(roleName,note) values (#{roleName},#{note})
    </insert>
    <delete id="deleteRole" parameterType="long">
        delete from t_role where id = #{id}
    </delete>
    <update id="updateRole" parameterType="role">
        update t_role set roleName = #{roleName}, note = #{note} where id = #{id}
    </update>
    <select id="getRole" parameterType="long" resultType="role">
        select id,roleName,note from t_role where id = #{id}
    </select>
    <select id="findRoles" parameterType="String" resultType="Role">
        select id,roleName,note from t_role where
        roleName like concat('%',#{roleName},'%')
    </select>
</mapper>

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>
    <typeAliases><!--别名-->
        <typeAlias alias="role" type="bean.Role"/>
    </typeAliases>
    <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/ssm_mybatis"/>
                <property name="username" value="root"/>
                <property name="password" value="wang"/>
            </dataSource>
        </environment>
    </environments>
    <!--映射文件-->
    <mappers>
        <mapper resource="Mapper/RoleMapper.xml"/>
    </mappers>
</configuration>

sqlsessionfactory创建：

package util;

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.IOException;
import java.io.InputStream;

public class SqlSessionFactoryUtils {
    //防止多线程中多次实例化
    private final static  Class<SqlSessionFactoryUtils> LOCK = SqlSessionFactoryUtils.class;

    private static SqlSessionFactory sqlSessionFactory = null;

    private SqlSessionFactoryUtils(){}

    public static SqlSessionFactory getSqlSessionFactory(){
        synchronized (LOCK){
            if (sqlSessionFactory != null){
                return sqlSessionFactory;
            }
            String res = "mybatis-config.xml";
            InputStream in;
            try {
                in = Resources.getResourceAsStream(res);
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
            }catch (IOException e){
                e.printStackTrace();
                return null;
            }
            return sqlSessionFactory;
        }
    }

    public static SqlSession openSqlsession(){
        if (sqlSessionFactory == null){
            getSqlSessionFactory();
        }
        return sqlSessionFactory.openSession();
    }
}

日志配置文件logr4:

log4j.rootLogger=DEBUG ,stdout
log4j.logger.org.mybatis=DEBUG
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p %d %C: %m%n

Client测试：

package test;

import Mapper.RoleMapper;
import bean.Role;
import org.apache.ibatis.session.SqlSession;
import org.apache.log4j.Logger;
import util.SqlSessionFactoryUtils;


public class Client {
    public static void main(String[] args){
        Logger logger = Logger.getLogger(Client.class);
        SqlSession sqlSession = null;
        try {
            sqlSession = SqlSessionFactoryUtils.openSqlsession();
            RoleMapper mapper = sqlSession.getMapper(RoleMapper.class);
            Role role = mapper.getRole(1L);
            logger.info(role.getRoleName());
        }finally {
            if (sqlSession!=null){
                sqlSession.close();
            }
        }
    }
}

result：