MyBatis3_轻松入门_final

MyBatis3

博文目录：

1. 缓存机制在MyBatis中的实现
2. MyBatis与Spring的整合

 缓存

在MyBatis使用缓存是非常简单的，只需要在UserMapper.xml中写一句话即可！！！

<?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.cn.mapper.UserMapper"> 
	<cache/>
	......

</mapper>

 

  配置了<cache/>这句话的映射有什么功效呢？

映射语句文件中所有的select语句将被缓存
映射语句文件中所有的insert,update,delete语句会刷新缓存
缓存会使用LRU（least recentily used：最近最少使用的）算法来回收
根据时间间隔来刷新缓存，默认不刷新
缓存会存储列表集合或对象的1024个引用
缓存被视为read/write的缓存

那么我们如何更改默认的缓存策略呢？

给cache标签添加相应的属性呗！

<cache eviction="FIFO" flushInterval="60000" size="512" readOnly="true"/>

 

  缓存根据FIFO算法回收，缓存更新的时间间隔为60s，存储512个引用，只读缓存

关于属性的配置信息如下：
回收策略：eviction
LRU:最近最少使用，移除相对来说较长时间不被使用的缓存（默认）
FIFO：先进先出，按进入缓存的顺序来移除缓存
SOFT：软引用，移除基于垃圾回收器状态和软引用规则的缓存
WEAK：弱引用，更积极的移除基于垃圾回收器状态和软引用规则的缓存

刷新间隔：flushInterval
毫秒数

引用数目：size
可以设置为任意正整数

只读：readOnly:true or false
默认是false，可读可写的

注意：
加入缓存后的POJO要实现序列化接口！！！
例如：
User.java

public class User implements Serializable{

	private static final long serialVersionUID = 1L;

}

 

  MyBatis与Spring的整合

当前的Sring版本未提供对MyBatis的支持

我们使用第三方jar包进行整合（mybatis-spring.jar）

下面简单说一下整合流程

pom.xml中需要的Jar包

<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.hyx</groupId>
  <artifactId>ibatis</artifactId>
  <packaging>war</packaging>
  <version>0.0.1-SNAPSHOT</version>
  <name>ibatis Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
    <dependency>
		<groupId>javax.servlet</groupId>
		<artifactId>jstl</artifactId>
		<version>1.2</version>
	</dependency>
	<dependency>
	  <groupId>javax.servlet</groupId>
	  <artifactId>servlet-api</artifactId>
	  <version>2.5</version>
	</dependency>
	<dependency>
		<groupId>org.springframework</groupId>
		<artifactId>spring-webmvc</artifactId>
		<version>3.2.4.RELEASE</version>
	</dependency>
	<dependency>
		<groupId>org.springframework</groupId>
		<artifactId>spring-jdbc</artifactId>
		<version>3.2.4.RELEASE</version>
	</dependency>
	
	<dependency>
			<groupId>org.codehaus.jackson</groupId>
			<artifactId>jackson-mapper-asl</artifactId>
			<version>1.9.10</version>
	</dependency>
	<dependency>
		<groupId>org.mybatis</groupId>
		<artifactId>mybatis</artifactId>
		<version>3.2.2</version>
	</dependency>
	<dependency>
		<groupId>org.mybatis</groupId>
		<artifactId>mybatis-spring</artifactId>
		<version>1.2.1</version>
	</dependency>          
	<dependency>
		<groupId>commons-dbcp</groupId>
		<artifactId>commons-dbcp</artifactId>
		<version>1.4</version>
	</dependency>
    <dependency>
		<groupId>mysql</groupId>
		<artifactId>mysql-connector-java</artifactId>
		<version>5.1.26</version>
	</dependency>
	<dependency>
		<groupId>javax.inject</groupId>
		<artifactId>javax.inject</artifactId>
		<version>1</version>
	</dependency>
    
  </dependencies>
  <build>
    <finalName>ibatis</finalName>
    <plugins>
    	<plugin>
		  <groupId>org.mortbay.jetty</groupId>
		  <artifactId>jetty-maven-plugin</artifactId>
		  <configuration>
		    <scanIntervalSeconds>10</scanIntervalSeconds>
		    <webApp>
		      <contextPath>/</contextPath>
		    </webApp>
		  </configuration>
		</plugin>
    </plugins>
  </build>
</project>

 

 jdbc.properties的配置

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc\:mysql\:///log
jdbc.username=root
jdbc.password=root

 

 spring和mybatis的配置 :applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
	
	<!-- spring的bean管理 -->
	<context:component-scan base-package="com.cct">
		<context:exclude-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
	</context:component-scan>
	
	<!-- 加载ClassPath中的properties文件 -->
	<context:property-placeholder location="classpath:jdbc.properties"/>
	<!-- 配置数据源 -->
	<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
		<property name="driverClassName" value="${jdbc.driver}"/>
		<property name="url" value="${jdbc.url}"/>
		<property name="username" value="${jdbc.username}"/>
		<property name="password" value="${jdbc.password}"/>
	</bean>
	
	<!-- 基于JDBC的事务管理器 -->
	<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
		<property name="dataSource" ref="dataSource"/>
	</bean>
	
	<tx:annotation-driven transaction-manager="transactionManager"/>
	
	<!-- 配置MyBatis  -->
	<bean id="sessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
		<property name="dataSource" ref="dataSource"/>
		<property name="typeAliasesPackage" value="com.cct.pojo"/>
	</bean>
	
	<!-- 自动扫描Mapper  -->
	<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
		<property name="basePackage" value = "com.cct.mapper"/> 
	</bean> 
	
</beans>

 

 web.xml中的配置

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
	xmlns="http://java.sun.com/xml/ns/javaee" 
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
	
<!-- SpringMVC 中央控制器 -->
  <servlet>
  	<servlet-name>mvc</servlet-name>
  	<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
  	<load-on-startup>1</load-on-startup>
  </servlet>
  
  <servlet-mapping>
  	<servlet-name>mvc</servlet-name>
  	<url-pattern>/</url-pattern>
  </servlet-mapping>
  
  <!-- Spring监听器 -->
  <context-param>
  	<param-name>contextConfigLocation</param-name>
  	<param-value>classpath:applicationContext*.xml</param-value>
  </context-param>
  <listener>
	<listener-class>
		org.springframework.web.context.ContextLoaderListener
	</listener-class>
  </listener>
	
  <display-name>Archetype Created Web Application</display-name>
</web-app>

  springmvc的配置文件：mvc-servlet.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:context="http://www.springframework.org/schema/context"
	xmlns:mvc="http://www.springframework.org/schema/mvc"
	xsi:schemaLocation="
	http://www.springframework.org/schema/beans
	http://www.springframework.org/schema/beans/spring-beans.xsd
	http://www.springframework.org/schema/context
	http://www.springframework.org/schema/context/spring-context.xsd
	http://www.springframework.org/schema/mvc
	http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">
	
	<context:component-scan base-package="com.cct.controller">
		<context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
	</context:component-scan>
	
	<mvc:annotation-driven/>
	
	<!-- 视图解析器 -->
	<bean id="viewResolver" class="org.springframework.web.servlet.view.UrlBasedViewResolver">
		<property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
		<property name="prefix" value="/WEB-INF/views/"/>
		<property name="suffix" value=".jsp"/>
	</bean>
	
</beans>

  com.cct.pojo.User

package com.cct.pojo;

public class User {

	private Integer id;
	private String username;
	private String password;
	
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	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;
	}
	
}

  com.cct.mapper.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.cct.mapper.UserMapper">

	<select id="findById" parameterType="int" resultType="User">
		select id,username,password from t_user where id=#{id}
	</select>
</mapper> 

  com.cct.mapper.UserMapper

package com.cct.mapper;

import com.cct.pojo.User;

public interface UserMapper {

	public User findById(int id);
}

  com.cct.service.UserService

package com.cct.service;

import javax.inject.Inject;
import javax.inject.Named;

import org.springframework.transaction.annotation.Transactional;

import com.cct.mapper.UserMapper;
import com.cct.pojo.User;

@Named
@Transactional
public class UserService {

	@Inject
	private UserMapper userMapper;
	
	public User findById(Integer id){
		return userMapper.findById(id);
	}
}

  com.cct.controller.UserController

package com.cct.controller;

import javax.inject.Inject;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;

import com.cct.pojo.User;
import com.cct.service.UserService;

@Controller
public class UserController {

	@Inject
	private UserService userService;
	
	@RequestMapping("/home/{id:\\d+}")
	public String show(@PathVariable int id,Model model){
		
		User user=userService.findById(id);
		model.addAttribute("user", user);
		return "home";
	}
}

  webapp/web-inf/views/home.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>My JSP 'home.jsp' starting page</title>
  </head>
  <body>
    <h1>hello,world!this is ${user.username }</h1>
  </body>
</html>

 

  启动服务其：jetty:run

输入：localhost:8080/home/1

显示：hello,world!this is jack