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Spring注入内部bean

   

正如你所知道的Java内部类是其他类的范围内定义的,同样,内部bean是被其他bean的范围内定义的bean。因此<property/>或<constructor-arg/>元素内<bean/>元件被称为内部bean和它如下所示。

 <?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-3.0.xsd">     <bean id="outerBean" class="...">       <property name="target">          <bean id="innerBean" class="..."/>       </property>    </bean>  </beans>

例如:

我们使用Eclipse IDE,然后按照下面的步骤来创建一个Spring应用程序:

步骤 描述
1 Create a project with a name SpringExample and create a package com.yiibai under the src folder in the created project.
2 Add required Spring libraries using Add External JARs option as explained in the Spring Hello World Example chapter.
3 Create Java classes TextEditorSpellChecker and MainApp under the com.yiibaipackage.
4 Create Beans configuration file Beans.xml under the src folder.
5 The final step is to create the content of all the Java files and Bean Configuration file and run the application as explained below.

这里是TextEditor.java文件的内容:

 package com.yiibai;  public class TextEditor {    private SpellChecker spellChecker;     // a setter method to inject the dependency.    public void setSpellChecker(SpellChecker spellChecker) {       System.out.println("Inside setSpellChecker." );       this.spellChecker = spellChecker;    }    // a getter method to return spellChecker    public SpellChecker getSpellChecker() {       return spellChecker;    }     public void spellCheck() {       spellChecker.checkSpelling();    } }

下面是另外一个相关的类文件SpellChecker.java内容:

 package com.yiibai;  public class SpellChecker {    public SpellChecker(){       System.out.println("Inside SpellChecker constructor." );    }     public void checkSpelling(){       System.out.println("Inside checkSpelling." );    }     }

以下是MainApp.java文件的内容:

 package com.yiibai;  import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext;  public class MainApp {    public static void main(String[] args) {       ApplicationContext context =               new ClassPathXmlApplicationContext("Beans.xml");        TextEditor te = (TextEditor) context.getBean("textEditor");        te.spellCheck();    } }

以下是配置文件beans.xml文件里面有配置为基于setter 注入,但使用内部bean:

 <?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-3.0.xsd">     <!-- Definition for textEditor bean using inner bean -->    <bean id="textEditor" class="com.yiibai.TextEditor">       <property name="spellChecker">          <bean id="spellChecker" class="com.yiibai.SpellChecker"/>        </property>    </bean>  </beans>

创建源代码和bean配置文件来完成,让我们运行应用程序。如果一切顺利,这将打印以下信息:

 Inside SpellChecker constructor. Inside setSpellChecker. Inside checkSpelling.
   
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