Spring Autowire byName无法按预期工作

Question

Spring autowire byName not working as expected.

public class SpellChecker {
    public SpellChecker() {
        System.out.println("Inside SpellChecker constructor." );
    }

    public void checkSpelling() {
        System.out.println("Inside checkSpelling." );
    }
}

public class TextEditor {

       private SpellChecker spellChecker1;
       private String name;

       public void setSpellChecker( SpellChecker spellChecker1 ){
          this.spellChecker1 = spellChecker1;
       }
       public SpellChecker getSpellChecker() {
          return spellChecker1;
       }
       public void setName(String name) {
          this.name = name;
       }
       public String getName() {
          return name;
       }

   public void spellCheck() {
       System.out.println(" TextEditor name is " +name);
      spellChecker1.checkSpelling();
   }
}

public class TextEditorMain {

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

        ApplicationContext context = new 
        ClassPathXmlApplicationContext("Beans.xml"); 
        TextEditor tEditor = (TextEditor) context.getBean("textEditor");
        tEditor.spellCheck();   
    }
}

Spring beans configuration:

<bean id = "spellChecker1" class = "com.spring.beans.SpellChecker">
</bean>

<bean id = "textEditor" class = "com.spring.beans.TextEditor" autowire="byName">
   <property name = "name" value = "text1"/>
</bean>

When I give spellChecker1 as bean id it is not working. Below are the console o/p,

Inside SpellChecker constructor.
 TextEditor name is text1
Exception in thread "main" java.lang.NullPointerException
    at com.spring.beans.TextEditor.spellCheck(TextEditor.java:26)
    at com.spring.main.TextEditorMain.main(TextEditorMain.java:15)

Bean id and reference name both are same spellChecker1 but still not working. But the strange thing is if I change the bean id in xml from spellChecker1 to spellChecker the code is working and giving below o/p,

Inside SpellChecker constructor.
 TextEditor name is text1
Inside checkSpelling.

So why dependency is not added when I am using spellChecker1 ?

Answer 1

It actually works as designed. Your property is named spellChecker not spellChecker1 . You have a field named spellChecker1 .

The name of the field is not the same as the name of a property . A name of the property is defined by the get and set methods available on a class. As you have a setSpellChecker (and the corresponding getter) there is a property named spellChecker .

All of this is written down in the JavaBeans Specification (which was written somewhere in 1998!)

Basically properties are named attributes associated with a bean that can be read or written by calling appropriate methods on the bean. Thus for example, a bean might have a foreground property that represents its foreground color. This property might be read by calling a Color getForeground() method and updated by calling a void setForeground(Color c) method.

Source the JavaBeans Specification.