Spring Loose Coupling example

Spring Loose Coupling example

The idea of object-oriented design is to divide the whole system into a set of reusable components, however, when the system gets bigger, especially in Java, the biggest object dependency will be tightly coupled so that it is very difficult to manage and modify, and now you can use the spring framework to play the role of an intermediate module, Easy and efficient management of other component dependencies

Example of output generation

For example, suppose your project has a way to output content to CSV or JSON format, you might write code like this

package com.mkyong.output;public interface IOutputGenerator{public void generateOutput();}

, and then the class that implements the interface

PackageCom.Mkyong.Output.Impl;ImportCom.Mkyong.Output.ioutputgenerator;public class  Csvoutputgenerator implements  Ioutputgenerator{public  void Generateoutput () { system.. Println ( "CSV Output Generator" }}          /span>                

And write a JSON-generated class.

PackageCom.Mkyong.Output.Impl;ImportCom.Mkyong.Output.ioutputgenerator;public class  Jsonoutputgenerator implements  Ioutputgenerator{public  void Generateoutput () { system.. Println "Json Output Generator" }}          /span>                

There are several ways to invoke the Ioutputgenerator interface, and how we can use spring to avoid over-coupling of objects.

Method 1-Call directly

PackageCom.Mkyong.Common;ImportCom.Mkyong.Output.Ioutputgenerator;ImportCom.Mkyong.Output.Impl.Csvoutputgenerator;Public Class App {public  static void main( String[] args )  { ioutputgenerator Output = new csvoutputgenerator(); output.  Generateoutput();  }}< /c14> 

Problem:

This method, output this object and csvoutputgenerator coupling together, every time to change the output format will have to modify the code, if this type of code throughout the project, then change up on the kneeling

method is called by the helper class

Maybe you'd like to create a helper class. All the output implementations are moved in

PackageCom.Mkyong.Output;ImportCom.Mkyong.Output.Ioutputgenerator;ImportCom.Mkyong.Output.Impl.Csvoutputgenerator;Public Class Outputhelper{ioutputgenerator Outputgeneratorpublic outputhelper () {outputgenerator = newcsvoutputgenerator (); }public void  Generateoutput () {outputgenerator.generateoutput (); }}          /span>                

You can then call this

PackageCom.Mkyong.Common;ImportCom.Mkyong.Output.Outputhelper;Public Class app { public  static void Main ( string[] args   { outputhelper output = newoutputhelper ();  Output.}}          /span>                

Problem:

It seems more elegant, you just need to manage this helper class to achieve different formats of output requirements change, however, helper or cvsoutputgenerator coupling, every time you want to change the output format, the helper class to do a fine tune.

Method 3-spring

Spring dependency Injection is appropriate to separate the different format generation classes

First, a little fine-tuning the outputhelper, adding a parameter

PackageCom.Mkyong.Output;ImportCom.Mkyong.Output.Ioutputgenerator;Public Class Outputhelper{IoutputgeneratorOutputgeneratorpublic void () {outputgenerator. Generateoutput}public void  Setoutputgenerator (ioutputgenerator Outputgeneratorthis. Outputgenerator = Outputgenerator;}}          /span>                

Then create a spring bean configuration file and declare that all Java objects depend on the

<!--Spring-common.xml--<beans xmlns="Http://www.springframework.org/schema/beans"Xmlns:xsi="Http://www.w3.org/2001/XMLSchema-instance"Xsi:schemalocation="Http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans-2.5.xsd"><bean Id="Outputhelper" Class="Com.mkyong.output.OutputHelper"><property Name="Outputgenerator" Ref="Csvoutputgenerator" /></bean><bean id= "csvoutputgenerator" class=" Com.mkyong.output.impl.CsvOutputGenerator " /><bean id=" Jsonoutputgenerator " class=" Com.mkyong.output.impl.JsonOutputGenerator " />  </beans>                

Then call through spring

PackageCom.Mkyong.Common;ImportOrg.Springframework.Context.ApplicationContext;ImportOrg.Springframework.Context.Support.Classpathxmlapplicationcontext;ImportCom.Mkyong.Output.Outputhelper;Public Class App { Public Static voidMain( String[]Args) { ApplicationContextContext= New classpathxmlapplicationcontext (new< Span class= "PLN" > string[] {  "spring-common.xml" });  outputhelper output = Span class= "pun" > (outputhelpercontextgetbean (. Generateoutput}}          /span>                

In the future to change the JSON format, directly change the XML configuration file on the line. Ability to reduce errors

Conclusion

With the spring framework's dependency injection, you can gracefully manage object dependencies with greater flexibility, especially for Java projects.

Spring Loose Coupling example (RPM)