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.javapackage 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;

@Component
public class Apple implements fruit{

@Override
public void info() {
// TODO Auto-generated method stub
System.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;
@Component
public class Assian implements people{

private fruit f;

@Autowired
public void setFruit(fruit f){
this.f = f;
}
@Override
public void eat() {
// TODO Auto-generated method stub
System.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 {

@Autowired
private people p;

@Test
public 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.*;

@Configuration
public class fruitConfig {

@Bean
public fruit apple(){
return new Apple("big");
}

@Bean
public 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;
}

@Override
public void info() {
// TODO Auto-generated method stub
System.out.println("a " + size + " apple");
}

}


Assian.java
package main;

public class Assian implements people{

private fruit f;

public Assian(fruit f){
this.f = f;
}
@Override
public void eat() {
// TODO Auto-generated method stub
System.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;
}

@Override
public void info() {
// TODO Auto-generated method stub
System.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;
}
@Override
public void eat() {
// TODO Auto-generated method stub
System.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")