Spring DI - Non-Static Factory


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Spring provides an option to inject dependency using factory-method along with factory-bean attributes in case of non-static factory methods.

Example

The following example shows a class TextEditor that can only be dependency-injected using pure setter-based injection.

Let's update the project created in Spring DI - Create Project chapter. We're adding following files −

  • TextEditor.java − A class containing a SpellChecker as dependency.

  • SpellChecker.java − A dependency class.

  • MainApp.java − Main application to run and test.

Here is the content of TextEditor.java file −

package com.tutorialspoint;

public class TextEditor {
   private SpellChecker spellChecker;
   private String name;
   
   public void setSpellChecker( SpellChecker spellChecker ){
      this.spellChecker = spellChecker;
   }
   public SpellChecker getSpellChecker() {
      return spellChecker;
   }
   public void setName(String name) {
      this.name = name;
   }
   public String getName() {
      return name;
   }
   public void spellCheck() {
      spellChecker.checkSpelling();
   }
}

Following is the content of another dependent class file SpellChecker.java

This class constructor is private. So its object can not be created directly using new operator by other object. It has a non-static factory method to get an instance.

package com.tutorialspoint;

public class SpellChecker {
   private SpellChecker(){
      System.out.println("Inside SpellChecker constructor." );
   }
   public SpellChecker getInstance() {
      System.out.println("Inside SpellChecker getInstance." );
      return new SpellChecker();
   }	
   public void checkSpelling(){
      System.out.println("Inside checkSpelling." );
   }
}

Following is the content of the MainApp.java file −

package com.tutorialspoint;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MainApp {
   public static void main(String[] args) {
      ApplicationContext context = new ClassPathXmlApplicationContext("applicationcontext.xml");
      TextEditor te = (TextEditor) context.getBean("textEditor");
      te.spellCheck();
   }
}

Following is the configuration file applicationcontext.xml which has configuration for autowiring byName

<?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 -->
   <bean id = "textEditor" class = "com.tutorialspoint.TextEditor" autowire = "byName">
      <property name = "name" value = "Generic Text Editor" />
   </bean>
   
   <bean id = "spellCheckFactory" class = "com.tutorialspoint.SpellChecker"></bean>

   <!-- Definition for spellChecker bean -->
   <bean id = "spellChecker" class = "com.tutorialspoint.SpellChecker" factory-method="getInstance">< factory-bean="spellCheckFactory"/bean>
</beans>

Output

Once you are done creating the source and bean configuration files, let us run the application. If everything is fine with your application, it will print the following message −

Inside SpellChecker constructor.
Inside SpellChecker getInstance.
Inside SpellChecker constructor.
Inside checkSpelling.
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