Spring 是一个 IOC(DI)和AOP的框架

Spring 是什么

• 轻量级，Spring是非侵入性的，基于Spring开发的应用中对象可以不依赖于Spring的API
• 依赖注入
• 面向切面编程
• 容器，Spring是一个容器，因为它包含并且管理应用对象的生命周期
• 框架，Spring实现了使用简单的组建配置组合成一个复杂的应用，在Spring中可以使用XML和Java的注解组合这些对象
• 一站式，在IOC和AOP的基础换行可以整合各种企业应用的开源框架和优秀的第三方类库，SpringMVC，Spring JDBC，Mybatis…

Spring Hello World

// src/com/lijunyang/model/HelloWorld.java
public class HelloWorld {
    private String name;
  public void setName(String name) {
      this.name = name;
  }
  public String getName() {
      return this.name;
  }
  public String hello() {
      System.out.println("Hello: " + this.name);
  }
}
// src/com/lijunyang/model/Main.java
public class Main {
    public static void main(String[] args) {
      HelloWorld hello = new HelloWorld();
    hello.setName("lijunyang");
    hello.hello();
    // "Hello: lijunyang"
  }
}

// src/applicationCentext.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"
    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-3.0.xsd">
    <bean id="helloWorld" class="com.lijunyang.model">
        <property name="name" value="Spring"></property>
    </bean>
</beans>
// src/com/lijunyang/model/Main.java
public class Main {
  public static void main(String[] args) {
    // 创建 Spring IOC容器
      org.springframework.context.ApplicationContext ctx = 
    new ClassPathXmlApplicationContext("applicationContext.xml");
    // 从容器中取出 Bean实例
    HelloWorld hello = (HelloWorld) ctx.getBean("helloWorld");
    hello.hello();
    // "Hello: Spring"
  }
}

// src/com/lijunyang/model/HelloWorld.java
public class HelloWorld {
    private String name;
  public HelloWorld() {
      System.out.println("HelloWorld`s Constructor");
  }
  public void setName(String name) {
    System.out.println("setName:" + name);
      this.name = name;
  }
  public String getName() {
      return this.name;
  }
  public String hello() {
      System.out.println("Hello: " + this.name);
  }
}
// src/com/lijunyang/model/Main.java
public class Main {
  public static void main(String[] args) {
      org.springframework.context.ApplicationContext ctx = 
    new ClassPathXmlApplicationContext("applicationContext.xml");
    // 此时输出
    // HelloWorld`s Constructor
    // setName: Spring
  }
}