Spring

优点

简化开发，降低企业级开发的复杂性

框架整合，高效整合其他技术，提高企业级应用开发与运行效率

核心概念

IoC（Inversion of Control）控制反转

使用对象时，由主动new产生对象转换为由外部提供对象，此过程中对象创建控制权由程序转移到外部，此思想称为控制反转

Bean

Ioc容器负责对象的创建、初始化等一系列工作，被创建或被管理的对象在Ioc容器中统称为Bean

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Spring框架的作用

SpringMVC处理请求，Mybatis操作数据库

Spring框架的作用是整合其他框架，让我们在项目中，把多个框架整合起来，用更少的代码实现项目功能。

Spring的环境搭建

创建项目导入jar包

<?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>com.yichen</groupId>
  <artifactId>spring01</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>war</packaging>

  <name>spring01 Maven Webapp</name>
  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
  </properties>

  <dependencies>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>servlet-api</artifactId>
      <version>3.0-alpha-1</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>commons-logging</groupId>
      <artifactId>commons-logging</artifactId>
      <version>1.2</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-aop</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-aspects</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-beans</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context-support</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-core</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-expression</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-instrument</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-instrument-tomcat</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-jdbc</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-jms</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-messaging</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-orm</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-oxm</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-oxm</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-test</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-tx</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-web</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc-portlet</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-websocket</artifactId>
      <version>4.1.6.RELEASE</version>
    </dependency>
  </dependencies>
  <build>
  </build>
</project>

配置Spring的配置文件

把springmvc.xml复制改名为spring.xml

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="
   http://www.springframework.org/schema/beans
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
   http://www.springframework.org/schema/context
   http://www.springframework.org/schema/context/spring-context-3.0.xsd
    http://www.springframework.org/schema/mvc
   http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">

    <bean id="user" class="com.yichen.pojo.User"></bean>

</beans>

SpringIOC

SpringIOC是spring的两大功能之一，SpringAOP。

SpringIOC是控制反转，其作用是把原来用new关键字创建对象，改成使用反射来创建对象。我们只需要在spring.xml配置文件中配置bean标签就可以把该bean标签中指定的类创建一个对象存放到SpringIOC的容器中。

Spring的IOC容器有两个，我们用的是ApplicationContext。其常用子类：ClassPathXMLApplicationContext

测试代码：

package com.hopu.test;

import com.hopu.pojo.User;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Demo {
    public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException {
        User user = new User();
        System.out.println(user);
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("spring.xml");
        User user1 = (User)context.getBean("user");
        System.out.println(user1);
        //反射
        Class<?> clazz = Class.forName("com.yichen.pojo.User");
        User user2 = (User)clazz.newInstance();
        System.out.println(user2);
    }
}