Spring的三种装配Bean的方式

Spring的三种装配Bean的方式

 

一．自动扫描+自动装配

适用情况：简单bean，初始化不需要基本bean之外的其他参数，无参构造函数或者仅需要其他bean，如果需要其他bean作为属性需要用@Autowired注入，需要事先定义好装配策略。

关键词：@Component：标识Bean，可被自动扫描发现

              @Configuration+ @ComponentScan(basepackages=”main”) : config.java文件中使用，制定扫描基本包，作为Spring上下文的配置文件。

              @Autowired：自动装配，查找容器中满足条件的Bean，注入。

 fruitConfig.java

package config;import org.springframework.context.annotation.ComponentScan;import org.springframework.context.annotation.Configuration;@Configuration@ComponentScan(basePackages="main")public class fruitConfig {}

fruit.java

package main;public interface fruit {public void info();}

Apple.java

package main;import org.springframework.stereotype.Component;@Componentpublic class Apple implements fruit{@Overridepublic void info() {// TODO Auto-generated method stubSystem.out.println("a  apple");}}

people.java

package main;public interface people {public void eat();}

Assian.java

package main;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Component;@Componentpublic class Assian implements people{private fruit f;@Autowiredpublic void setFruit(fruit f){this.f = f;}@Overridepublic void eat() {// TODO Auto-generated method stubSystem.out.print("i am a assian, i am eating ");f.info();}}

testMethod.java

package main;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.test.context.ContextConfiguration;import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;@RunWith(SpringJUnit4ClassRunner.class)@ContextConfiguration(classes=config.fruitConfig.class)public class testMethod {@Autowiredprivate people p;@Testpublic void test1(){p.eat();}}

二．通过java代码装配bean

适用情况：所有情况基本适用，区别方法一：不需要事先定义好装配策略，因为会在config.java中定义。

关键词：@Configuration + @Bean：创建config.java，并定义bean的获取方法且需要用@Bean注释，需要注入其他Bean作为参数不需要使用@Autowired。

              @Autowired：自动装配，查找容器中的Bean，注入。

 

fruitConfig.java

package config;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import main.*;@Configurationpublic class fruitConfig {@Beanpublic fruit apple(){return new Apple("big");}@Beanpublic people assian(fruit f){return new Assian(f);}}

Apple.java

package main;public class Apple implements fruit{private String size;public Apple(String size){this.size = size;}@Overridepublic void info() {// TODO Auto-generated method stubSystem.out.println("a " + size +  " apple");}}

Assian.java

package main;public class Assian implements people{private fruit f;public Assian(fruit f){this.f = f;}@Overridepublic void eat() {// TODO Auto-generated method stubSystem.out.print("i am a assian, i am eating ");f.info();}}

测试类同上：

三．通过XML装配bean

使用情况：大部分情况。

关键词：<bean>及其子元素。

Apple.java

package main;public class Apple implements fruit{private String size;public Apple(String size){this.size = size;}@Overridepublic void info() {// TODO Auto-generated method stubSystem.out.println("a " + size +  " apple");}}

Assian.java

package main;import java.util.List;public class Assian implements people{private fruit f;private List<String> fruitlist;public Assian(fruit f, List<String> fruitlist){this.f = f;this.fruitlist = fruitlist;}@Overridepublic void eat() {// TODO Auto-generated method stubSystem.out.print("i am a assian, i am eating ");f.info();for(String s : fruitlist){System.out.println(s);}}}

config.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"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"><bean id="apple" class="main.Apple"><constructor-arg value="big"></constructor-arg></bean><bean id="assian" class="main.Assian"><constructor-arg ref="apple"></constructor-arg><constructor-arg><list><value>1</value><value>2</value><value>3</value><value>4</value><value>5</value></list></constructor-arg></bean></beans>

fruitConfig.java

package config;import org.springframework.context.annotation.Configuration;import org.springframework.context.annotation.ImportResource;@Configuration@ImportResource("config/config.xml")public class fruitConfig {}

该config文件设计java配置和XML配置的混合配置的方法。

@ImportResource("config/config.xml")