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();
}
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");
}
}
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：
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");
}
}
package main;
import java.util.List;
public class Assian implements people{
private fruit f;
private List fruitlist;
public Assian(fruit f, List 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
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package config;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.ImportResource;
@Configuration
@ImportResource("config/config.xml")
public class fruitConfig {
}
@ImportResource("config/config.xml")