Java 为什么@Autowired annotation将同一类的每个bean关联到context.xml中？

Context.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-3.0.xsd
http://www.springframework.org/schema/context 
http://www.springframework.org/schema/context/spring-context-3.0.xsd">

<context:annotation-config />

<bean id="foo" class="annotation.Foo">
    <property name="name" value="firstFoo"></property>
</bean>
<bean id="secondaryFoo" class="annotation.Foo">
    <property name="name" value="secondaryFoo"></property>
    <qualifier value="secondaryFoo"></qualifier>
</bean>
<bean id="bar" class="annotation.Bar" />

Foo:

public class Bar {

@Autowired
@Qualifier(value="secondaryFoo")
private Foo foo;

public void setFoo(Foo foo) {
    this.foo = foo;
}
public void  printFooName(){
    System.out.println("\nBar class: foo.getName(): "+foo.getName()+"\n");      
}

}

public class Foo {
private String name;

public Foo(){
    System.out.println("\nFoo class: Constructor invoked, name: "+ name + "\n");
}

public void setName(String name) {
    this.name = name;
}

public String getName() {
    return name;
}

@PostConstruct
public void init() {
    System.out.println("\nFoo class: @PostConstruct Bean Foo successfully initialized, name: " + name +"\n");
}
@PreDestroy
public void cleanUp() {
    System.out.println("*\nFoo class: @PreDestroy clean up called\n");
}
}

public class TestFooBar {

public static void main(String[] args) throws InterruptedException {

    System.out.println("\nMain invoked\n");

    AbstractApplicationContext applicationContext = 
            new ClassPathXmlApplicationContext("annotation/annotation.xml");

    Bar bar = applicationContext.getBean("bar", Bar.class);

    bar.printFooName();

}

}

Main:

public class Bar {

@Autowired
@Qualifier(value="secondaryFoo")
private Foo foo;

public void setFoo(Foo foo) {
    this.foo = foo;
}
public void  printFooName(){
    System.out.println("\nBar class: foo.getName(): "+foo.getName()+"\n");      
}

}

public class Foo {
private String name;

public Foo(){
    System.out.println("\nFoo class: Constructor invoked, name: "+ name + "\n");
}

public void setName(String name) {
    this.name = name;
}

public String getName() {
    return name;
}

@PostConstruct
public void init() {
    System.out.println("\nFoo class: @PostConstruct Bean Foo successfully initialized, name: " + name +"\n");
}
@PreDestroy
public void cleanUp() {
    System.out.println("*\nFoo class: @PreDestroy clean up called\n");
}
}

public class TestFooBar {

public static void main(String[] args) throws InterruptedException {

    System.out.println("\nMain invoked\n");

    AbstractApplicationContext applicationContext = 
            new ClassPathXmlApplicationContext("annotation/annotation.xml");

    Bar bar = applicationContext.getBean("bar", Bar.class);

    bar.printFooName();

}

}

运行应用程序时，系统输出按以下顺序打印：

- Main invoked 
- Foo class: Constructor invoked, name: null 
- Foo class: @PostConstruct Bean Foo successfully initialized, name: firstFoo 
- Foo class: Constructor invoked, name: null 
- Foo class: @PostConstruct Bean Foo successfully initialized, name: secondaryFoo 
- Bar class: foo.getName(): secondaryFoo

如果我在Bar类（@Autowired@Qualifier（value=“secondary Foo”））中指定了具有secondary Foo id的bean，那么为什么在te上下文中，这两个bean都被实例化

---

如果我删除这两个注释，系统输出的结果是相同的！这怎么可能

在

annotation.xml

上下文中指定两个

Foo

bean，因此Spring会实例化这两个bean（以及

bar

bean）

然后，它将

secondaryFoo

作为依赖项注入到

bar

bean中

---

如果您不想自动创建bean，您可以像这样在

annotation.xml

中将它们声明为

lazy init=“true”

<代码>。。。使用lazy=“true”时，Spring给了我这个错误：org.springframework.beans.factory.xml.xmlbeandefinitionstoreexception，但我看到使用lazy属性时，bean的实例化是相同的。区别仅在于实例化的顺序。对吗？我只需要实例化firstFoo。这是可能的吗？如果你只想让firstFoo实例化，你希望注入到bar中的是什么？lazyinit将延迟初始化，直到需要它为止，即注入另一个bean或从上下文中查找。如果您将第一个和第二个foo都声明为lazy，那么由于您没有在任何地方使用firstFoo，所以应该实例化它。希望有帮助。