empty tag – if the requested variable is greater than or equal to the specified value then this tag is used to evaluate the contents contained in the nested body parts of this tag.

Logic greaterThan Tag (<logic: greaterThan>…
</ logic:greaterThan>) 

greaterThan Tag : Tag evaluation of the nested body content occurs only if the specified value is greater than the specified value.

This tag compares the variable against the specified constant value. If the variable is greater than  the specified value then the nested body contents of this tag is evaluated

Attributes of greaterThan Tag

Example Illustrating the use of the Logic greaterEqual Tag<logic:greaterEqual> and the Logic greaterThan Tag<logic:greaterThan> .

Here you will learn to use the Struts  Logic tags. We will cover an example that will show  a comparison between  the two logic tags (ie..&lt$$logic:greaterEqual> and the <logic:greaterThan>).

Example code

Creating an Action  Class

Develop a simple action class LogicAction.java.

Creating Form Bean

Our form bean class contains only one property number. Here is the code of FormBean (LogicForm.java)

Defining form Bean in struts-config.xml file

Add the following entry in the struts-config.xml file for defining the form bean

 Developing the Action Mapping in the struts-config.xml

Here, Action mapping helps to select the method from the Action class for specific requests.

Developing the InputLogic.jsp page

Developing the output.jsp page

Add the following line in the index.jsp to call the form.

<li>
<html:link page=”/pages/InputLogic.jsp”>Struts File Upload</html:link>
<br>
Example demonstrates  how LogicAction Class works.
</li>

Building and Testing the Example 

To build and deploy the application go to Struts\Strutstutorial directory and type ant on the command prompt. This will deploy the application. Open the browser and navigate to the InputLogic.jsp page. Your browser displays the following  page.

Entering a number greater than 1 and less than 10000  to the InputLogic.jsp page evaluates the working of the <logic:greaterEqual> tag

It displays the following out.jsp page

Writing a number greater than 10000 to the InputLogic.jsp displays

The output.jsp displays the working of the both tags.

equal tag – if the requested variable is equal to the specified value then this tag is used to evaluate the contents contained in the nested body parts of this tag.

Logic notEqual Tag (<logic:notEqual >…</logic:notEqual>) 

notEmpty – if the requested variable is not equal to the specified value then this tag is used to evaluate the contents contained in the nested body parts of this tag.

Compares the variable passed against the specified constant value. The nested body content of this tag is evaluated if the variable and value are not equal.

Attributes of notEmpty Tag

Example Illustrating the use of the Equal<logic:equal> and the notEqual <logic:notEqual> logic tags.

Here you will learn to use the Struts  Logic  Equal and notEqual tags. We will cover an example that will show  a comparison between  the two logic tags (ie..<logic:equal > and the <logic:notEqual >).

Example code

Creating an Action  Class

Develop a simple action class LogicAction.java.

Creating Form Bean

Our form bean class contains only one property number. Here is the code of FormBean (LogicForm.java)

Defining form Bean in struts-config.xml file

Add the following entry in the struts-config.xml file for defining the form bean

 Developing the Action Mapping in the struts-config.xml

Here, Action mapping helps to select the method from the Action class for specific requests.

Developing the InputLogic.jsp page

Developing the output.jsp page

Add the following line in the index.jsp to call the form.

<li>
<html:link page=”/pages/InputLogic.jsp”>Struts File Upload</html:link>
<br>
Example demonstrates  how LogicAction Class works.
</li>

Building and Testing the Example 

To build and deploy the application go to Struts\Strutstutorial directory and type ant on the command prompt. This will deploy the application. Open the browser and navigate to the InputLogic.jsp page. Your browser displays the following  page.

Writing value equal to1 to the InputLogic.jsp page displays the working of  the  Equal Logic tag <logic:equal > 

It displays the following out.jsp page

Now  write any data other than 1 to the InputLogic.jsp to see the working of  the notEqual logic tag <logic:notEqual>

The <logic:notEqual > evaluated here displays the output.jsp as

Herbert Schildt
    Teach Yourself C++
    Java: The Complete Reference, J2SE
    Struts: the complete reference
O’Reilly
    .NET & XML
    ADO.NET in a Nutshell
    ADO: ActiveX Data Objects

Create a new struts 1.1 project to to understand nested tags.

Object Class Books
Create a class Books with properties id and name in the package roseindia.web.common.
Add a getter and setter method for each property.
Also add  a constructor that initialize the properties.

Books.java

package roseindia.web.common;

public class Books {

	private int id;

	private String name;
	//constructors

	public Books(){}
	public Books(int id, String name){

		this.id = id;

		this.name = name;

	}

	public int getId() {

		return id;

	}

	public void setId(int id) {

		this.id = id;

	}

	public String getName() {

		return name;

	}

	public void setName(String name) {

		this.name = name;

	}

}

Object Class Authors
Create a second java class Authors in the same package roseindia.web.common.
Add two properties, id of type int and name of type String and one property books of type Collection, which holds a list of books.
Add a getter and setter method for each property.
Also add  a constructor that initialize the properties.

Authors.java

package roseindia.web.common;

import java.util.*;

public class Authors {

	

	private int id;

	private String name;

	

	//books collection

	private Collection books;

	

	//constructors

	public Authors() {}

	public Authors(int id, String name, Collection books){

		this.id = id;

		this.name = name;

		this.books = books;

	}

	public Collection getBooks() {

		return books;

	}

	public void setBooks(Collection books) {

		this.books = books;

	}

	public int getId() {

		return id;

	}

	public void setId(int id) {

		this.id = id;

	}

	public String getName() {

		return name;

	}

	public void setName(String name) {

		this.name = name;

	}

}

Action form class AuthorsBooksForm
Create a java class AuthorsBooksForm in the package roseindia.web.struts.form, which extends the class ActionForm of struts.
Add a property authors of type Authors .
Add a getter and setter method for the property authors .

Implement the reset() method of the ActionForm class. 

AuthorsBooksForm.java

package roseindia.web.struts.form;

import java.util.*;

import org.apache.struts.action.ActionForm;

import org.apache.struts.action.ActionMapping;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import roseindia.web.common.Authors;

import roseindia.web.common.Books;

public class AuthorsBooksForm extends ActionForm {

	Authors authors;

	public void setAuthors(Authors authors) {

		this.authors = authors;

	}

	public Authors getAuthors() {

		return authors;

	}

	

	public void reset(ActionMapping mapping,HttpServletRequest request) {

		

		//initial a dummy collection of books

		Collection books = new ArrayList();

		

		books.add(new Books(1, “Teach Yourself C++”));

		books.add(new Books(2, “Java: The Complete Reference, J2SE”));

		books.add(new Books(3, “Struts: The Complete Reference”));

		//initial a dummy authors

		authors = new Authors(1, “Herbert Schildt”, books);

		

	}

}

Action class AuthorsBooksAction 

Create a java class AuthorsBooksAction in the package roseindia.web.struts.action, which extends the class Action of struts.
Return the forward example.

AuthorsBooksAction.java

package roseindia.web.struts.action;

import roseindia.web.struts.form.AuthorsBooksForm;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.util.*;

import org.apache.struts.action.Action;

import org.apache.struts.action.ActionForm;

import org.apache.struts.action.ActionForward;

import org.apache.struts.action.ActionMapping;

public class AuthorsBooksAction extends Action {

	

	public ActionForward execute(

		ActionMapping mapping,

		ActionForm form,

		HttpServletRequest request,

		HttpServletResponse response) {

		AuthorsBooksForm booksForm = (AuthorsBooksForm) form;

		

		return mapping.findForward(“books”);

	}

}

The JSP file

Create a new JSP file authorsbooks.jsp.
Add the reference to the tag library nested at the top of the file.

authorsbooks.jsp

<%@ page language=”java”%>

<%@ taglib uri=”/tags/struts-bean” prefix=”bean” %>

<%@ taglib uri=”/tags/struts-html” prefix=”html” %>

<%@ taglib uri=”/tags/struts-logic” prefix=”logic” %>

<%@ taglib uri=”/tags/struts-nested” prefix=”nested”%>

 

<html>

	<head>

		<title>Struts nested tag Example</title>

	</head>

	<body>

	  <h1>Struts nested tag Example</h1>

	  <b>Author and his books:</b>

		<html:form action=”/example” method=”post”> 

			<nested:nest property=”authors”>

				

				<b><nested:write property=”name”/> </b>

				<nested:iterate property=”books”>

						

					<ul><li><nested:write property=”name”/></li></ul>

				</nested:iterate>

			</nested:nest>

			

		</html:form>

	</body>

</html>

Configure the struts-config.xml

Open the struts-config.xml and add the form bean and action mapping.

struts-config.xml

 <form-beans>

  	<form-bean name=”AuthorsBooksForm”

		 type=”roseindia.web.struts.form.AuthorsBooksForm” />

 </form-beans>

<action-mappings>

         <action

            path=”/example”

            type=”roseindia.web.struts.action.AuthorsBooksAction”

            input=”/pages/user/authorsbooks.jsp”

            name=”AuthorsBooksForm”

            scope=”request”

            validate=”false”>

            <forward name=”example” path=”/pages/user/authorsbooks.jsp” />

        </action>

</action-mappings>

Output:
To view the output run the authorsbooks.jsp from the browser.

This article shows you how to develop custom Struts PlugIn and incorporate in your Struts Web Applications. After completing this tutorial you will be able to create your own custom PlugIn for your web application. Struts PlugIn allows the programmer to enhance their web applications. There are many PlugIns available for struts e.g. Struts Tiles PlugIn, Struts Hibernate PlugIn, Struts Spring PlugIn etc. Beside these available PlugIn you can create your own PlugIn.

Understanding PlugIn

Struts PlugIns are configured using the <plug-in> element within the Struts configuration file. This element has only one valid attribute, ‘className’, which is the fully qualified name of the Java class which implements the org.apache.struts.action.PlugIn interface.

For PlugIns that require configuration themselves, the nested <set-property> element is available.

The plug-in tag in the struts-config.xml file is used to declare the PlugIn to be loaded at the time of server start-up. Following example shows how to declare the Tiles PlugIn:

<plug-in className=”org.apache.struts.tiles.TilesPlugin”>
    <set-property
        property=”definitions-config”
           value=”/WEB-INF/tiles-defs.xml”/>
</plug-in>

The above declaration instructs the struts to load and initialize the Tiles plugin for your application on startup. 

Writing Struts PlugIn Java Code

In this example we write HelloWorld Struts PlugIn example that will give you idea about creating, configuring and checking Struts PlugIn. Our HelloWorld Stuts PlugIn contains a method called Say Hello, which simply returns HelloWorld message.

Here is code of HelloWorld Struts Plugin: 

Configuring PlugIn

To configure the plugin add the following line your struts-config.xml file.

<plug-in className=”roseindia.net.plugin.HelloWorldStrutsPlugin”>
</plug-in>

Calling PlugIn From JSP Page

Here is the code for calling our PlugIn from jsp page.

Building and Testing

Use ant tool to build the application and then deploy on the server. Enter the url http://localhost:8080/strutstutorial/pages/plugin.jsp in your browser. It display “Hello Plugin” message. Your server console also should display “Hello Plugin” message.

In this section we learnt how to develop simple struts plugin, configure, deploy and test.

Above query creates test table and then populates the table with data.

Configuring Struts Application
Now create a directory “strutsdatabase” in the jakarta-tomcat-5.5.9\webapps\ directory and copy the content of struts-blank application (unzipped above) in the strutsdatabase directory.

Now start the tomcat and try to access the strutsdatabase application by typing the url http://localhost:8080/strutsdatabase in browser. Your browser should display the welcome page. After testing shutdown the tomcat server.

Configuring Struts DataSource Manager
The Struts DataSource manager makes it easy for your Action class get the database connection. To configure the Stuts DataSource Manager we will uncomment the <data-sources> entry in the struts-config.xml.

Uncomment and then <data-sources> entry in the struts-config.xml and then change the line

“org.apache.commons.dbcp.BasicDataSource” to “org.apache.tomcat.dbcp.dbcp.BasicDataSource“. In tomcat 5.5.9 dbcp classes are packaged in naming-factory-dbcp.jar archieve, so we are using “org.apache.tomcat.dbcp.dbcp.BasicDataSource” instead of “org.apache.commons.dbcp.BasicDataSource”. After this change the database dirver, database url and passwor in the <data-sources> tag.

You <data-source> element should look like:

<data-sources>

<data-source type=”org.apache.tomcat.dbcp.dbcp.BasicDataSource“>

    <set-property

      property=”driverClassName”

      value=”com.mysql.jdbc.Driver” />

    <set-property

      property=”url”

      value=”jdbc:mysql://localhost:3306/strutsdatabase?autoReconnect=true” />

    <set-property

      property=”username”

      value=”root” />

    <set-property

      property=”password”

      value=”” />

    <set-property

      property=”maxActive”

      value=”10″ />

    <set-property

      property=”maxWait”

      value=”5000″ />

    <set-property

      property=”defaultAutoCommit”

      value=”false” />

    <set-property

      property=”defaultReadOnly”

      value=”false” />

    <set-property

      property=”validationQuery”

      value=”SELECT COUNT(*) FROM test” />

</data-source>

</data-sources>

        

Create action Class to Test the DataSource
Now we will write the code of Action class for getting the connection form DataSource:

Following code is used to get the data source and then connection from Struts DataSource:

dataSource = getDataSource(request);
myConnection = dataSource.getConnection();

Save this file(TestDataSource.java)  into jakarta-tomcat-5.5.9\webapps\strutsdatabase\WEB-INF\src\java\test directory. Add the servlet API into class path. Then open dos prompt and navigate to jakarta-tomcat-5.5.9\webapps\strutsdatabase\WEB-INF\src\ directory and issue run ant. This will compile the action class (TestDataSource.java) and copy it to the classes directory of the webapplication.

Creating Action Mapping struts-config.xml
Now add the following action mapping into the struts-config.xml:

Running and testing
Start tomcat and browse the url http://localhost:8080/strutsdatabase/DataSource.do. Your browser should show the following output.

Now check tomcat console, it should display records fetched from database.

You can download my struts-config.xml from here.

Note: The DataSource manager is being retained in Struts 1.x for backward compatibility but may not be retained in Struts 2.x or later.