Spring AOP and Annotation based AspectJ

The concept

Recently I had to work on a requirement that asked that logs be kept when anyone performs certain actions upon the database.

For example if some chose to remove an item from the database – the action, who performed it, when it was performed and any extra information should be noted in the database.

Implementing this can be performed in a variety of ways. We could have simply told developers to call a function within any database methods to log the action. However Spring AOP provides a better way of doing this.

The idea

To make it easier to store the logs I wanted users to simply be able to annotate any methods they felt needed logging in the message.

Then using AspectJ we would have code that would intercept the methods and log the action in the database. All developers would need to do is very simply annotate their methods.

The Annotation

First of all I had to create the Java Method annotation that can be placed above the required methods.

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
 
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface LogAction {
	String actionPerformed();
}

The annotation simply has one parameter that allows the developer to specify the action performed such as ‘object deleted’ etc.

The aspect class

Next was to write the Spring aspect class which will perform the actual logging of the action

First of all we write a simple class and add the @Aspect annotation before the class

@Aspect
public class MyAspect

Next we need to define the Pointcut. As a Spring defintion a Pointcut is:

Pointcut: a predicate that matches join points. Advice is associated with a pointcut expression and runs at any join point matched by the pointcut (for example, the execution of a method with a certain name). The concept of join points as matched by pointcut expressions is central to AOP, and Spring uses the AspectJ pointcut expression language by default.

I’m writing a simple point cut that matches any public methods. This is coded like so:

@Pointcut(value="execution(public * *(..))")
public void anyPublicMethod() { }

The last part of the Aspect class is the Advice. Spring defines the advice as:

Advice: action taken by an aspect at a particular join point. Different types of advice include “around,” “before” and “after” advice. Many AOP frameworks, including Spring, model an advice as an interceptor, maintaining a chain of interceptors around the join point.

I need my advice to handle the “around” advice and only methods with my @LogAction annotation

To do this I used the following method:

@Around("anyPublicMethod() && @annotation(logAction)")
public Object logAction(ProceedingJoinPoint pjp, LogAction logAction) throws Throwable {
}

The method uses my anyPublicMethod Pointcut and the @annotation(logAction) to match only public methods with the LogAction annotation specified.

I have also included the ProceedingJoinPoint parameter so I can access the various arguments in the annotated method.

The final Aspect class is as follows:

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
 
@Aspect
public class MyAspect{
 
	@Pointcut(value="execution(public * *(..))")
	public void anyPublicMethod() {
	}
 
	@Around("anyPublicMethod() && @annotation(logAction)")
	public Object logAction(ProceedingJoinPoint pjp, LogAction logAction) throws Throwable {
 
		// Do what you want with the actionperformed
		String actionPerformed = logAction.actionPerformed();
 
		// Do what you want with the join point arguments
		for ( Object object : pjp.getArgs()) {
			System.out.println(object);
		}
 
		return pjp.proceed();
	}
}

Updating the Spring app config

To ensure that our @Aspect annotated class is picked up by Spring you simply need to add the following to your app-config.xml

<aop:aspectj-autoproxy/>
<bean id="myAspect" class="package.to.my.MyAspect" />

This assumes that you have the aop namespace within your app-config beans definition like so

<?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:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
                           http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">
 
.....
 
</beans>

Setting up intercepted methods

The final step is to mark the methods we want to be intercepted

This is as easy as doing the following

@LogAction(actionPerformed="doSomething")
public void doSomething(MyObject someParameter) {
}

Now whenever that method is executed we will firstly execute our Aspect code.

Spring Forms and Dynamic Binding Lists

Introduction

After my recent posts on Spring forms and annotations – dynamic lists is logically another step to be discussed.

In the previous examples we use a form backing object – the form backing objects have tended to be very basic and primitive

Using dynamic lists within these objects makes them slightly more complicated. Suppose the following scenario:

Class enrolment example

• User chooses to create a new class
• User types in class name
• User also has to specify one (or many) names of students in the class

Using that scenario you can imagine a form in which there is a class name field and then below that a simple student name field. When the user clicks add next to the student name – javascript should simply show another input field for a student name allowing a user to add one or more students.

Eventually when the form gets submitted to the server a list of students will be populated.

However if we don’t using Spring’s dynamic lists – specifically Spring’s AutoPopulatingList – we cannot perform such an action as we have out of bounds errors.

Configuring your build environment

Your workspace needs setting up as the previous examples. Using Eclipse create a new project. For your src directory enter the value /WEB-INF/src. For your output directory use the WEB-INF/classes directory.

Add a new lib directory in your WEB-INF folder. Under your WEB-INF directoy you will need the following JAR files (all of which can be obtained from the Spring download). Add the jars to your buildpath.

commons-beanutils.jar
commons-collections.jar
jstl.jar
spring-core.jar
spring-webmvc.jar
spring.jar
standard.jar
tiles-api-2.0.6.jar
tiles-core-2.0.6.jar
tiles-jsp-2.0.6.jar

Next add the Spring servlet.xml to your application. Create a file called dynamiclists-servlet.xml in your WEB-INF folder. Add the following to the file:

<?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:p="http://www.springframework.org/schema/p"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans 
                           http://www.springframework.org/schema/beans/spring-beans.xsd
                           http://www.springframework.org/schema/context 
                           http://www.springframework.org/schema/context/spring-context.xsd">
 
 
 
    <context:component-scan base-package="com.annotations.controller" />
    <bean class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping"/>
    <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"/>
 
    <!-- Enables plain Controllers -->
    <bean class="org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter" />
 
    <bean id="tilesConfigurer" class="org.springframework.web.servlet.view.tiles2.TilesConfigurer">
        <property name="definitions">
	    <list>
		<value>/WEB-INF/tiles-defs/templates.xml</value>
	    </list>
	</property>
    </bean>
 
    <bean id="viewResolver" class="org.springframework.web.servlet.view.UrlBasedViewResolver">
	<property name="viewClass" value="org.springframework.web.servlet.view.tiles2.TilesView"/>
    </bean>                
</beans>

Next add your web.xml in the same location as your Spring servlet.xml file. Add the following contents:

<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app version="2.4"
		 xmlns="http://java.sun.com/xml/ns/j2ee"
		 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
		 xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
 
	<display-name>Spring Dynamic Lists Example</display-name>
 
 
	<servlet>
		<servlet-name>dynamiclists</servlet-name>
        	<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        	<load-on-startup>1</load-on-startup>
	</servlet>
 
	<servlet-mapping>
    		<servlet-name>dynamiclists</servlet-name>
    		<url-pattern>*.page</url-pattern>
    	</servlet-mapping>
 
 
</web-app>

Next add a new folder in your WEB-INF directory called tiles-defs and add a file called templates.xml within that. Add the following to the templates.xml file

<?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE tiles-definitions PUBLIC
       "-//Apache Software Foundation//DTD Tiles Configuration 2.0//EN"
       "http://tiles.apache.org/dtds/tiles-config_2_0.dtd">
 
<tiles-definitions>
 
	<definition name="form.view" template="/pages/form.jsp">
	</definition>
 
	<definition name="formStudentInsert.view" template="/pages/formStudentInsert.jsp">
	</definition>
 
	<definition name="formResult.view" template="/pages/formResult.jsp">
	</definition>
 
</tiles-definitions>

That should be the workspace setup – next to create our form JSP pages

Form JSP pages and a touch of jQuery

Firstly create a new folder under your application called js. Next download jQuery and place the jQuery download within the folder.

Under your project create a new folder names pages and create a file named form.jsp within that.This will be our class creation form.

Add the following to your form.jsp file

<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<%@ taglib uri="http://www.springframework.org/tags" prefix="spring" %>
 
<script type="text/javascript" src="/dynamiclists/js/jquery-1.3.2.min.js"></script>
<script type="text/javascript">
$(document).ready(function() {
	var studentPosition = 0;
	$("#addStudentButton").click(function() {
		studentPosition++;
 
		$.get("<%=request.getContextPath()%>/appendStudentView.page", { fieldId: studentPosition},
			function(data){
				$("#submitRow").before(data);
		});
	});
});
</script>
 
<form:form method="post" name="classForm" id="classForm" commandName="classCommand">
	<table>
		<tr>
			<td>Class Name:</td>
			<td colspan="2"><form:input path="className" size="40" /></td>
		</tr>
		<tr>
			<td colspan="3"><strong>Students</strong></td>
		</tr>
		<tr>
			<td>Student name</td>
			<td>
				<spring:bind path="classCommand.students[0].studentName">
					<form:input path="${status.expression}" size="40" />
	  			</spring:bind>
			</td>
			<td><input type="button" id="addStudentButton" value="Add" /></td>
		</tr>
		<tr id="submitRow">
			<td>&nbsp;</td>
			<td><input type="submit" value="Save Class" /></td>
		</tr>
	</table>
</form:form>

This probably requires a bit of an explanation. The first two lines of the file include the required Spring tag libraries.

After that we include the link to our downloaded jQuery Javascript source. I’ll make an assumption that people are familiar with jQuery.

Next we use jQuery to add a click event listener to our form ‘Add’ button. When the user clicks add button we fire off an Ajax Get request to our server which sends an incremented number as part of its data string. This Ajax request hits our server which simply appends a new row to the form for another student name. We use the number for the index number in the collection of students.

The response is simply appended as a new row in our form before the form submit button. After that Javascript the rest is a basic Spring form.

Next create a new file called formStudentInsert.jsp in the same location as your form.jsp and add the following contents.

<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<%@ taglib uri="http://www.springframework.org/tags" prefix="spring" %>
 
<tr>
	<td>&nbsp;</td>
	<td>
		<form:input path="classCommand.students[${studentNumber}].studentName" size="40" />
	</td>
	<td>&nbsp;</td>
</tr>

As mentioned before this is JSP that gets appended to our form when we send the Ajax request.

The form should look similar to the image below.

Next create a JSP page that is displayed when the user submits the form. Create a new JSP called formResult.jsp and add the following contents.

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
 
<h2>Class ${savedClass.className}</h2>
 
<p>Students</p>
 
<ul>
	<c:forEach var="student" items="${savedClass.students}">
		<li>${student.studentName}</li>
	</c:forEach>
</ul>

The Form Backing Object

We next need to create the form backing objects that will be used for this example. Create a new Java class called Student and add the following contents:

/**
 * @author Eggsy - eggsy _at_ eggsylife.co.uk
 *
 */
public class Student{
	private String studentName = null;
 
	public String getStudentName() {
		return studentName;
	}
 
	public void setStudentName(String studentName) {
		this.studentName = studentName;
	}
 
}

This class is a simple Student object. Student objects will belong to a class object. Now we can go ahead and create the Class object.

Create a new class called ClassCommand and add the following:

import org.springframework.util.AutoPopulatingList;
 
/**
 * @author Eggsy - eggsy _at_ eggsylife.co.uk
 *
 */
public class ClassCommand {
	private String className = null;
	private AutoPopulatingList students = null;
 
 
	public String getClassName() {
		return className;
	}
 
	public void setClassName(String className) {
		this.className = className;
	}
 
	public AutoPopulatingList getStudents() {
		return students;
	}
 
	public void setStudents(AutoPopulatingList students) {
		this.students = students;
	}
}

The class command object is the backing object we shall use for our form. It simply has a class name. However it does also have a list of students. For this we could have used a basic java.util.ArrayList but this causes issues when attempting to bind the form. As the list wouldn’t (initially) have any contents we would experience IndexOutOfBounds exception messages. This is where we can use the incredibly helpful Spring AutopopulatingList.

Spring Annotated Form Controller

Finally we need to create the Spring Form controller that handles our various requests. Note in the servlet XML file we specified that we would scan the package com.annotations.controller package for controller annotations. Go ahead and create this package. (You can of course change this). Now create a class called ClassFormController containing the following:

import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.util.AutoPopulatingList;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
 
import com.annotations.command.ClassCommand;
import com.annotations.command.Student;
 
 
/**
 * @author Eggsy - eggsy _at_ eggsylife.co.uk
 */
@Controller
public class ClassFormController
{
 
	@ModelAttribute("classCommand")
    	public ClassCommand getClassCommand()
    	{
		ClassCommand classCommand = new ClassCommand();
		classCommand.setStudents(new AutoPopulatingList(Student.class));
		return classCommand;
    	}
 
	/**
	 * <p>Called when the form is initially displayed</p>
	 * @param model
	 * @return
	 */
	@RequestMapping(method = RequestMethod.GET, value="/processClassForm.page")
	protected String showNameForm(ModelMap model)
	{	
		return "form.view";
	}
 
	/**
	 * <p>Called when the user clicks the add button</p>
	 * @param fieldId
	 * @param model
	 * @return
	 */
	@RequestMapping(method = RequestMethod.GET, value="/appendStudentView.page")
	protected String appendStudentField(@RequestParam Integer fieldId, ModelMap model)
	{	
		model.addAttribute("studentNumber", fieldId);
		return "formStudentInsert.view";
	}
 
	/**
	 * <p>Called when the user finally submits the class form</p>
	 * @param classCommand
	 * @param model
	 * @return
	 */
	@RequestMapping(method = RequestMethod.POST, value="/processClassForm.page")
	protected String onSubmit( @ModelAttribute("classCommand") ClassCommand classCommand,  ModelMap model )
	{
		model.addAttribute("savedClass", classCommand);
		return "formResult.view";
	}
 
}

I’ll assume you’re comfortable with Spring annotations so I’ll just highlight the important parts. Firstly notice the way we declare our ClassCommand object. We new up the object then set the Students list as a new AutoPopulatingList of type Student.class. This is again so that we can ensure we experience no IndexOutOfBounds errors. The next method is called when we display our form simply returning the form.view. After that we have the method that gets called when the user clicks the Add button. This returns the small HTMl snippet that gets appended to our form. Finally we have the onSubmit method that gets called when we submit our form and returns the formResult view.

Ok so thats pretty much it. If you followed the examples word for word you after setting up your web application you should be able to visit http://localhost:8080/dynamiclists/processClassForm.page and test your web app.

You can also download the example project here within the project there is a docs folder that also includes a sample Tomcat context file for application deployment.

References: http://blog.richardadamdean.com/?page_id=119

Any comments or questions are always welcome!

In one of my previous posts we documented how to implement Spring Annotations with a form. If you haven’t got a copy of the project from that post you can grab it here.

Building on that example this guide shows how, using Spring and jQuery, you can Ajaxify your forms so that when submitted the user doesn’t have to be redirected to a new page

jQuery and required plugins

Create a new folder in the root of your project and call it ‘js’

Then grab a copy of jQuery. The minified version will be fine. Add the jQuery javascript file to your ‘js’ folder.

Currently it is at version 1.3.2 so I have a file called jquery-1.3.2.min.js in my js folder

Next download a very useful plugin the jQuery Form Plugin. Also place the plugin in your js folder.

Linking your JS

Open the form.jsp file and add the following lines:

<script type="text/javascript" src="/annotations/js/jquery-1.3.2.min.js"></script>
<script type="text/javascript" src="/annotations/js/jquery.form.js"></script>

Here we are linking to the two jQuery javascript files we have just downloaded. Note I reference /annotations/ that is my application name yours may however be different.

Convert the form to Ajax

This step involves using the jQuery form plugin to make your form submit via Ajax. After including the scripts add the following code:

<script type="text/javascript">
	$(document).ready(function() { 
		var formOptions = {target: '#nameFormResponse'};
		$('#nameForm').ajaxForm(formOptions);
	});
</script>

This assumes you are quite comfortable with jQuery but just to explain, in the above code we are saying that when the document is read fetch the form with the id of nameForm and convert it to an ajaxForm (The ajaxForm function is built into the form plugin we download). We are also specifying some options for the ajaxForm method namely the target. A target is an jQuery selector that the Ajax Form plugin will automatically populate with the response from your submit

After your form go ahead and add in the div with the same id as the target, in the case above id=”nameFormResponse”.

The whole form.jsp should now look like so:

<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
 
<script type="text/javascript" src="/annotations/js/jquery-1.3.2.min.js"></script>
<script type="text/javascript" src="/annotations/js/jquery.form.js"></script>
 
<script type="text/javascript">
	$(document).ready(function() { 
		var formOptions = {target: '#nameFormResponse'};
		$('#nameForm').ajaxForm(formOptions);
	});
</script>
 
 
<form:form method="post" name="nameForm" id="nameForm" commandName="nameCommand">
	<table>
		<tr>
			<td>Name:</td>
			<td><form:input path="name" size="40" /></td>
		</tr>
		<tr>
			<td>&nbsp;</td>
			<td><input type="submit" value="Send my name" /></td>
		</tr>
	</table>
</form:form>
 
<div id="nameFormResponse">
</div>

That should be it – so now if you visit http://localhost:8080/annotations/processName.page and submit the form you will see that the page doesn’t change and we render the response of the form submit into our nameFormResponse div element.

You can grab a copy of this project here

In case anyone was wondering after reading the previous Spring Annotations guide you can also user various parameters to get hold of the current logged in user.

To get hold of the user principal simply add a new parameter to your Request annotated methods called:

org.springframework.web.context.request.WebRequest myWebRequest

Using the previous tutorial as an example your method should look like something similar to this:

@SuppressWarnings("unchecked")
@RequestMapping(method = RequestMethod.GET)
protected String showNameForm(WebRequest webRequest, ModelMap model) throws Exception
{	
	String username = webRequest.getUserPrincipal().getName();
	//Do what you need with the username
	return "form.view";
}

Since the release of Spring 2.5, the framework has allowed for MVC annotations for mapping your URL’s to your various controllers.

This tutorial gives an example of how the annotations can be used within your application.

Grab the Spring Framework

First of all grab the latest stable release of Spring (version 2.5.6)

I’m going to assume you’re comfortable in creating Web Application Java projects using Eclipse so I’ll ignore this step.

Configuring your build path

We simply need to add the following JAR’s to our build path. Add the Jars into your lib directory.

commons-beanutils.jar
commons-collections.jar
commons-digester.jar
jstl.jar
spring.jar
spring-core.jar
spring-webmvc.jar
standard.jar
tiles-api-2.0.6.jar
tiles-core-2.0.6.jar
tiles-jsp-2.0.6.jar

Note: This is the minimum amount of required libs for this example and all Jars can be taken from the Spring Framework download lib and dist directories.

JSP Form page creation

If you haven’t already create a new folder in your project called pages and add a file in it called form.jsp (Of course depending on configuration you can name the files however you like.

Add the following to the form.jsp file. This creates the simple JSP page that is our form

<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
 
<form:form method="post" name="nameForm" id="nameForm" commandName="nameCommand">
	<table>
		<tr>
			<td>Name:</td>
			<td><form:input path="name" size="40" /></td>
		</tr>
		<tr>
			<td>&nbsp;</td>
			<td><input type="submit" value="Send my name" /></td>
		</tr>
	</table>
</form:form>

In the JSP you can see I’m using the Spring frameworks form tag library. Also note we specify and commandName, if you haven’t already encountered this – that is important. We specify the nameCommand and we shall be using that later.

Now add another JSP called formResult.jsp. This is the JSP that gets displayed when the form has been submitted. Add the following code:

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
 
<p>${formResult}</p>

Configuring the web.xml

Next we can move onto the web.xml and what setup requirements we need to make our Web application work with Spring MVC

If you haven’t already create a web.xml file in your WEB-INF folder

Add the following into your web.xml

<?xml version="1.0" encoding="ISO-8859-1"?>
 
<web-app version="2.4"
		 xmlns="http://java.sun.com/xml/ns/j2ee"
		 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
		 xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
 
	<display-name>Spring Annotations Example</display-name>
 
 
	<servlet>
		<servlet-name>annotations</servlet-name>
                <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
                <load-on-startup>1</load-on-startup>
       </servlet>
 
	<servlet-mapping>
    	        <servlet-name>annotations</servlet-name>
    	         <url-pattern>*.page</url-pattern>
        </servlet-mapping>
 
        <listener>
  	         <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
	</listener>
 
	<context-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>classpath:applicationContext.xml</param-value>
	</context-param>
</web-app>

To explain we’re going to create a web application under the context name annotations and then we’re mapping the Spring DispatcherServlet to it and Spring will handle any URL’s ending in .page

Again depending on configuration this doesn’t have to be .page it can be something of your choice.

Tiles configuration

For this example I am using Tiles for the ‘View’ part of our MVC

Under the WEB-INF folder create a new directory called ’tiles-defs’ and add a file in it called ‘templates.xml’.

Add the following to your templates.xml file

<?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE tiles-definitions PUBLIC
       "-//Apache Software Foundation//DTD Tiles Configuration 2.0//EN"
       "http://tiles.apache.org/dtds/tiles-config_2_0.dtd">
 
<tiles-definitions>
 
	<definition name="form.view" template="/pages/form.jsp">
	</definition>
 
        <definition name="formResult.view" template="/pages/formResult.jsp">
	</definition>
 
 
</tiles-definitions>

Very basically we are defining a new View called form.view that relates to our previously created form.jsp page and formResult.view that maps to the formResult.jsp

Spring MVC Servlet.xml

Now we can configure the Spring MVC servlet.xml file. Create a new file called annotations-servlet.xml and place it in the WEB-INF directory. (The same place as the web.xml.

Note: we call the file annotations-servlet.xml because of the servlet mapping named using in our web.xml – you can of course change this.

Add the following to the file

<?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:p="http://www.springframework.org/schema/p"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans 
                           http://www.springframework.org/schema/beans/spring-beans.xsd
                           http://www.springframework.org/schema/context 
                           http://www.springframework.org/schema/context/spring-context.xsd">
 
 
 
	<context:component-scan base-package="com.annotations.controller" />
        <bean class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping"/>
	<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"/>
 
	<!-- Enables plain Controllers -->
        <bean class="org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter" />
 
        <bean id="tilesConfigurer" class="org.springframework.web.servlet.view.tiles2.TilesConfigurer">
	    <property name="definitions">
                <list>
		    <value>/WEB-INF/tiles-defs/templates.xml</value>
		</list>
	    </property>
	</bean>
 
	<bean id="viewResolver" class="org.springframework.web.servlet.view.UrlBasedViewResolver">
		<property name="viewClass" value="org.springframework.web.servlet.view.tiles2.TilesView"/>
	</bean>                
</beans>

This file sets up a few things – firstly you’ll notice that we use the context-component scan – this means that Spring will look through the package we specify for any annotations which means when we annotate our URL’s they will work. In this example I scan the com.annotations.controller package. We also setup the Spring annotation handlers.

The items after that basically configure our view resolver which in our case is Tiles and we specify the location of the templates.xml file we created in the previous steps

A bit of business logic

To make the tutorial a bit more relevant I’m going to include Springs applicationContext.xml file which would generally include a web applications database/business logic beans.

In the WEB-INF/src folder create a new file called ‘applicationContext.xml’

Add the following:

<?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-2.5.xsd">
 
	<bean id="businessBean" class="com.annotations.business.BusinessLogicBeanImpl">
	</bean>
</beans>

Just define one business logic bean com.annotations.business.BusinessLogicBeanImpl which will code next.

The business logic bean

Go ahead and create and create a new java package under the path com.annotations.business

Add a new <<Interface>> into this class called BusinessLogicBean and add the following code:

package com.annotations.business;
 
/**
 * @author Eggsy - eggsy_at_eggsylife.co.uk
 */
public interface BusinessLogicBean
{
	public String processName(String name);
}

We’re defining a single business logic method that will handle the name the user has entered and do something with it

Create a new class in the same package called BusinessLogicBeanImpl and make it implement the BusinessLogicBean interface.

package com.annotations.business;
 
/**
 * @author Eggsy - eggsy_at_eggsylife.co.uk
 */
public class BusinessLogicBeanImpl implements BusinessLogicBean
{
	/* (non-Javadoc)
	 * @see com.annotations.business.BusinessLogicBean#processName(java.lang.String)
	 */
	public String processName(String name)
	{
		if( name.equals("admin"))
		{
			return "Hello admin welcome";
		}
		else
		{
			return "Hey you're not admin but Hi to " + name + " anyway!!";
		}
	}
}

I’ve defined a pretty useless business method but feel free to change this

The Form command Object

On the form JSP file in the form we mentioned an attribute called commandName and we gave it a value of nameCommand. This basically tells Spring what object to use behind the form. We can now go ahead and create that object.

Create a new package called com.annotations.command and place a new class in it called NameCommand. Add the following code:

package com.annotations.command;
 
/**
 * @author Eggsy - eggsy_at_eggsylife.co.uk
 */
public class NameCommand
{
	private String name = null;
 
	/**
	 * @return the name
	 */
	public String getName()
	{
		return name;
	}
 
	/**
	 * @param name the name to set
	 */
	public void setName(String name)
	{
		this.name = name;
	}
}

Notice we have one class variable called name this maps to the name input field on our form

Finally…the annotated controller

If you remember in the servlet.xml file we stated that we would scan the com.annotations.controller package. Go ahead and create this package.

In the package create a new class called NameFormController

Just before the class defintion add the following annotations:

@Controller
@RequestMapping("/processName.page")

The annotations mean that this controller will map any URL’s matching processName.page

Next within the class add a variable that is our BusinessLogicBean. Add the lines:

@Autowired
protected BusinessLogicBean businessBean = null;

This introduces another annotation the @Autowired, this means Spring will automatically inject this object for us. Note the bean is given the name businessBean this identically matches our definition in the applicationContext file

Next we setup the form backing object which if you remember was the NameCommand this is done with a few more annotations like so:

@ModelAttribute("nameCommand")
public NameCommand getProductCommand()
{
    NameCommand nameCommand = new NameCommand();
    return nameCommand;
}

Again notice that tie we use an annotation of @ModelAttribute and give it a name of nameCommand which is used by the form on our JSP.

Next up is to add the annotated get method. This is the method that renders the view which should display the form.

@SuppressWarnings("unchecked")
@RequestMapping(method = RequestMethod.GET)
protected String showNameForm(ModelMap model) throws Exception
{	
	return "form.view";
}

Important to notice here is that we return “form.view” which matches the tiles definition we created earlier. Also note that we use the @RequestMapping method and we map this to the GET which is called to display the form

Finally we can go ahead and write the method that handles the form submit. Add the following to the class:

@RequestMapping(method = RequestMethod.POST)
protected String onSubmit( @ModelAttribute("nameCommand") NameCommand nameCommand,  ModelMap model )
{
	String formResult = businessBean.processName(nameCommand.getName());
	model.addAttribute("formResult", formResult);
	return "formResult.view";
}

This method is slightly more complex. As before we use the @RequestMapping annotation but this time we map it to the POST. In the parameters however we use the @ModelAttribute annotation again but this time it specifies that from the form being submitted we will have a populated nameCommand object. Using our business logic bean we process the name entered.

If you remember the formResult.jsp we simply output an item called $formResult, using our model object we add the formResult to the model so that the JSP is able to access this and then we simply return the formResult tiles view

The whole class should look like this:

package com.annotations.controller;
 
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
 
import com.annotations.business.BusinessLogicBean;
import com.annotations.command.NameCommand;
 
 
/**
 * @author Eggsy - eggsy_at_eggsylife.co.uk
 */
@Controller
@RequestMapping("/processName.page")
public class NameFormController
{
    @Autowired
    protected BusinessLogicBean businessBean = null;
 
    @ModelAttribute("nameCommand")
    public NameCommand getProductCommand()
    {
        NameCommand nameCommand = new NameCommand();
	return nameCommand;
    }
 
    @SuppressWarnings("unchecked")
    @RequestMapping(method = RequestMethod.GET)
    protected String showNameForm(ModelMap model) throws Exception
    {	
        return "form.view";
    }
 
    @RequestMapping(method = RequestMethod.POST)
    protected String onSubmit( @ModelAttribute("nameCommand") NameCommand nameCommand,  ModelMap model )
    {
        String formResult = businessBean.processName(nameCommand.getName());
	model.addAttribute("formResult", formResult);
	return "formResult.view";
    }
}

Testing…

Phew that should be it – assuming you have setup your application the same as mine and have configured your server environment such as Tomcat if you visit http://localhost:8080/annotations/processName.page you should see the form. Try submitting the form and you should see the response as dictated by our business logic.