【Mybatis】- 工做流程

ORM:Object Relation Mapping：对象关系映射，通俗理解就是将一个对象相关属性和数据库数据进行关联(映射)，传统咱们对数据库数据的操做能够经过ORM框架转移到对对象的操做上来，这无疑有利于提升程序的开发效率和项目的可维护性，本质是对传统的JDBC操做高级封装

工做流程

mybatis经过sqlSessionFactory建立sqlSession, sqlSession表示应用程序与数据库的会话，当用户使用mapper.xml文件中配置的的方法时，mybatis首先会解析sql动态标签为对应数据库sql的形式，并将其封装进MapperStatement对象，而后经过executor将sql注入数据库执行，并返回结果

常见ORM框架：hibernate、mybatis

mybatis主要经过两个配置文件(sqlMapConfig.xml和Mapper.xml)，来配置数据库和对象的关系

sqlMapConfig.xml

Mybatis全局配置文件，主要配置mybatis的环境参数、映射对象运行参数。

mybatis的环境参数：数据源配置、事务控制

映射对象运行参数：映射对象的别名设置、映射对象配置文件加载

案例：

<?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>
    
<!-- 加载数据库属性文件：db.properties -->
<properties resource="db.properties"/>
 
<!-- 
     typeAliases:别名设置
     package:mybatis自动扫描polo类，自动建立别名(类型名)
 -->
<typeAliases>
   <typeAlias type="com.zhiwei.domain.User" alias="user"/>
   <package name="com.zhiwei.domain" />
</typeAliases>

<!-- 和spring整合environment配置将抛弃 -->
<environments default="development">
<environment id="development">
    
<!-- 使用jdbc事务管理 -->
<transactionManager type="JDBC"/>

<!-- 数据链接池 :mybatis管理-->
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driver}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.user}"/>
<property name="password" value="${jdbc.password}"/>
</dataSource>
</environment>
</environments>

<!-- 加载映射文件
     resource:每次只能加载一个文件
     class:只能mapper代理对象执行(mapper接口名和mapper.xml文件名一致，而且在同一个目录)
     package:批量加载：name为mapper文件所在的包名
 -->
<mappers>
   <mapper resource="com/zhiwei/domain/UserMapper.xml"/>
</mappers>
</configuration>

mapper.xml:主要配置映射对象在数据库中相关的操做

案例：

<?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命令空间：sql访问地址划分 -->
<mapper namespace="test">
<!-- 映射文件配置sql语句 ：select执行数据库查询
id:sql语句封装mappedStatement的id
#{id}:占位符,表示接受输入的参数：id，若是输入参数类型为简单类型，
#{}中的参数名能够任意，
resultType:返回结果类型
-->
<select id="findUserById" parameterType="int" resultType="user">
select *from user where id=#{id}
</select>

<delete id="deleteUserById" parameterType="int">
delete from user where id=#{id}
</delete>

<!-- 若是输入的参数为pojo类型，占位符名称使用pojo的属性 -->
<update id="updateUser" parameterType="com.zhiwei.domain.User">
update  user set name=#{name},passwd=#{passwd} where id=#{id}
</update>

<insert id="addUser" parameterType="com.zhiwei.domain.User">
insert into user(id,name,passwd) values(#{id},#{name},#{passwd})
</insert>
</mapper>

mapper.xml对应的对象：

package com.zhiwei.domain;
public class User {
	private int id;
	private String name;
	private String passwd;
	
	public User(){}
	public User(int id, String name, String passwd) {
		super();
		this.id = id;
		this.name = name;
		this.passwd = passwd;
	}

	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 getPasswd() {
		return passwd;
	}
	public void setPasswd(String passwd) {
		this.passwd = passwd;
	}
	@Override
	public String toString() {
		return "User [id=" + id + ", name=" + name + ", passwd=" + passwd + "]";
	}
}

sqlSession工具类：

package com.zhiwei.tool;

import java.io.IOException;
import java.io.InputStream;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

/**
 * Mybatis工具类
 * @author Yang Zhiwei
 */
public final class MybatisTool {
   
	private static InputStream is=null;
	private static SqlSession sqlSession=null;
	
	/**
	 * 获取Mybstis SqlSession会话
	 * @return
	 */
    public static SqlSession getSession(){
    	
	 try {
		is=Resources.getResourceAsStream("SqlMapConfig.xml");
	} catch (IOException e) {
		e.printStackTrace();
	}
	
	/**本质经过调用DefaultSqlSessionFactory建立sqlSession
	 *DefaultSqlSession:与数据库进行JDBC操做的类
	 *   MappedStatement：与JDBC操做的StateMent类相似，封装sql信息，
	 *   mybatis的动态sql标签在提交给数据库以前会进行sql的规范化，控制台日志显示
	 *   executor：真正和数据库进行交互的执行者
	 *   configuration：mybatis配置文件信息的封装类
	 *部分源码：
	 *   @Override
		  public int update(String statement, Object parameter) {
		    try {
		      dirty = true;
		      MappedStatement ms = configuration.getMappedStatement(statement);
		      return executor.update(ms, wrapCollection(parameter));
		    } catch (Exception e) {
		      throw ExceptionFactory.wrapException("Error updating database.  Cause: " + e, e);
		    } finally {
		      ErrorContext.instance().reset();
		    }
		  }
	 *   
	 * */
	//经过mybatis的控制文件建立sqlSessionFactory
	SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(is);
	sqlSession=sqlSessionFactory.openSession(); 
	return sqlSession;
    }
   
    /**
     * 关闭mybatis SqlSession会话
     */
    public static void resourceClosing(){
    	try{
    	if(sqlSession!=null){
    		sqlSession.close();
    	}
    	if(is!=null){
    	   is.close();
    	}
    	}catch (Exception e) {
			e.printStackTrace();
		}
    }
}

对象的操做方法接口(方法名必须与Mapper.xml文件中sql的Id对应，mybatis没法正确解析)：

package com.zhiwei.service;

import org.apache.ibatis.session.SqlSession;

import com.zhiwei.domain.User;
import com.zhiwei.tool.MybatisTool;

/***
 * 基础服务类
 * @author Yang Zhiwei
 */
public  class BasicServiceImp{
    
	private static SqlSession sqlSession=null;
	
	//SqlSession初始化
	static{
		sqlSession=MybatisTool.getSession();
	}
	
	/**
	 * 经过Id查询用户信息
	 * test:表示命名空间  
	 * findUserById:mapper.xml文件的动态sql id
	 * test.findUserById:指明访问动态sql地址--->对应：<mapper namespace="test">
	 * @param id
	 * @return
	 */
	public static User findUserById(int id) {
		return sqlSession.selectOne("test.findUserById", id);
	}

	/**
	 * 更新用户信息
	 * @param user
	 */
	public static void updateUser(User user) {
		sqlSession.update("test.updateUser",user);
		sqlSession.commit();
		MybatisTool.resourceClosing();
	}

	/**
	 * 删除用户信息
	 * @param id
	 */
	public static void deleteUserById(int id) {
		sqlSession.delete("test.deleteUserById", id);
		sqlSession.commit();
		MybatisTool.resourceClosing();
	}

	/**
	 * 添加用户信息
	 * @param user
	 */
	public static void addUser(User user) {
		sqlSession.insert("test.addUser",user);
		sqlSession.commit();   
		MybatisTool.resourceClosing();
	}
}

测试类：

package com.zhiwei.test;

import com.zhiwei.domain.User;
import com.zhiwei.service.BasicServiceImp;

public class BasicTest {

	public static void main(String[] args) {
		
		User user=BasicServiceImp.findUserById(1);
		System.out.println(user);
	}
}

结果：

DEBUG [main] - Logging initialized using 'class org.apache.ibatis.logging.log4j.Log4jImpl' adapter.
DEBUG [main] - Class not found: org.jboss.vfs.VFS
DEBUG [main] - JBoss 6 VFS API is not available in this environment.
DEBUG [main] - Class not found: org.jboss.vfs.VirtualFile
DEBUG [main] - VFS implementation org.apache.ibatis.io.JBoss6VFS is not valid in this environment.
DEBUG [main] - Using VFS adapter org.apache.ibatis.io.DefaultVFS
DEBUG [main] - Find JAR URL: file:/D:/BaiduYunDownload/mybatis/bin/com/zhiwei/domain
DEBUG [main] - Not a JAR: file:/D:/BaiduYunDownload/mybatis/bin/com/zhiwei/domain
DEBUG [main] - Reader entry: User.class
DEBUG [main] - Reader entry: UserMapper.xml
DEBUG [main] - Listing file:/D:/BaiduYunDownload/mybatis/bin/com/zhiwei/domain
DEBUG [main] - Find JAR URL: file:/D:/BaiduYunDownload/mybatis/bin/com/zhiwei/domain/User.class
DEBUG [main] - Not a JAR: file:/D:/BaiduYunDownload/mybatis/bin/com/zhiwei/domain/User.class
DEBUG [main] - Find JAR URL: file:/D:/BaiduYunDownload/mybatis/bin/com/zhiwei/domain/UserMapper.xml
DEBUG [main] - Not a JAR: file:/D:/BaiduYunDownload/mybatis/bin/com/zhiwei/domain/UserMapper.xml
DEBUG [main] - Reader entry: <?xml version="1.0" encoding="utf-8"?>
DEBUG [main] - Checking to see if class com.zhiwei.domain.User matches criteria [is assignable to Object]
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - PooledDataSource forcefully closed/removed all connections.
DEBUG [main] - Openning JDBC Connection
DEBUG [main] - Created connection 1211076369.
DEBUG [main] - ooo Using Connection [com.mysql.jdbc.JDBC4Connection@482f8f11]
DEBUG [main] - ==>  Preparing: select *from user where id=? 
DEBUG [main] - ==> Parameters: 1(Integer)
User [id=1, name=zhangsan, passwd=zhangsan]

日志分析：从Log4J的控制台日志能够清楚看到，mybatis的本质就是JDBC操做， 对数据库数据的操做就能够直接经过像调用普通方法同样进行，很是方便

数据库数据: