（007）spring容器获取ApplicationContext

　　spring容器获取ApplicationContext几种方法

1、使用@Autowired注解

　　pom.xml

<?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.edu.spring</groupId>
    <artifactId>spring</artifactId>
    <version>1.0.0</version>

    <name>spring</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>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
    
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>4.3.2.RELEASE</version>
        </dependency>
    </dependencies>

</project>

　　User.java

package com.edu.spring;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Component;

@Component
public class User {

    @Autowired
    private ApplicationContext applicationContext;
    
    public void show(){
        System.out.println("user: "+applicationContext);
    }
    
}

　　App.java

package com.edu.spring;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class App {

    public static void main(String[] args) {
        AnnotationConfigApplicationContext context=new AnnotationConfigApplicationContext("com.edu.spring");
        context.getBean("user",User.class).show();
        context.close();
    }
}

　　运行结果如下：

 2、实现ApplicationContextAware接口，在set方法中赋值

　　Book.java

package com.edu.spring2;

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

@Component
public class Book implements ApplicationContextAware {

    private ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext)
            throws BeansException {
        // TODO Auto-generated method stub
        this.applicationContext=applicationContext;
    }
    
    public void show(){
        System.out.println("book :"+applicationContext.getClass());
    }
}

　　App.java

package com.edu.spring;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class App {

    public static void main(String[] args) {
        AnnotationConfigApplicationContext context=new AnnotationConfigApplicationContext("com.edu.spring");
        context.getBean("book",Book.class).show();
        context.close();
    }
}

　　运行结果如下：

  3、在构造函数中赋值（spring4.3中新特性），有局限性，只能有一个构造函数，如果有多个构造函数，会选择默认的无参的构造函数

　　Bank.java

package com.edu.spring;

import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Component;

@Component
public class Bank {

    private ApplicationContext applicationContext;
    
    public Bank(ApplicationContext applicationContext){
        this.applicationContext=applicationContext;
    }
    
    public  void show(){
        System.out.println("bank: "+applicationContext.getClass());
    }
}

　　App.java

package com.edu.spring;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class App {

    public static void main(String[] args) {
        AnnotationConfigApplicationContext context=new AnnotationConfigApplicationContext("com.edu.spring");
        context.getBean("bank",Bank.class).show();
        context.close();
    }
}

　　运行结果如下：