JSP Standard Actions

JSP actions are special XML tags which control the behavior of servlet engine. JSP actions allow you to insert a file dynamically, reuse external JavaBean components, forward the request to the other page and generate HTML for Java Applet Plugin.

jsp:include action

JSP include action allows you to include a file at runtime. The syntax of JSP include action is as follows:

1	<jsp:include page="Relative URL" flush="true" />

In the page attribute, you insert a relative URL of a file which could be an HTML file or another JSP page. Unlike the include directive, the jsp include action insert a file at the time page is being requested.

jsp:useBean action

JSP useBean action lets you load a JavaBean component into the page and use it later. JSP useBean action allows you to reuse other Java classes. The syntax of JSP useBean action is as follows:

1	<jsp:useBean id="objectName" class="package.class" />

By using the jsp:useBean action, you create a new object with the object nameobjectName of the class package.class. Later on, you can access the properties of this object by using either jsp:setProperty or jsp:getProperty. Let’s take a look at an example. First, we have a JavaBeans call Message:

public class Message {

private String text;

/**

* @return the text

public String getText() {

return text;

}

/**

* @param text the text to set

public void setText(String text) {

this.text = text;

}

Then we create a JSP page which uses the jsp:useBean action to access JavaBean Message inside that page.

<html>

<head>

<title>jsp:useBean Demo</title>

</head>

<body>

<jsp:useBean id="msg"

class="com.jsptutorial.Message" />

<jsp:setProperty name="msg"

property="text"

value="JSP useBean Demo" />

<h1>

<jsp:getProperty name="msg"

property="text" />

</h1>

</body>

</html>

We use jsp:setProperty to set the text property of the JavaBean Message and then we call jsp:getProperty to get that message and print it out. Here is the output screenshot:

jsp:forward Action

jsp:forward action allows you to forward a request to the other page. The syntax of the jsp:forward action is listed as below. There is one attribute called page which value is a page you want to forward the request to. You can specify the page statically or dynamically by using the expression.

1 2	<jsp:forward page="error.jsp" /> <jsp:forward page="<%= java-expression %>" />

jsp:plugin Action

jsp:plugin action allows you to embedded Java Applet into a page. Suppose you have an applet which demonstrates the JSP page life cycle called com.jsp.jspapplet. Here is the way we use jsp:plugin action to embedded that applet into a page:

<html>

<head>

<title>jsp:plugin Demo</title>

</head>

<body>

<jsp:plugin type="applet"

code="com.jsp.jspapplet"

codebase="."

width="500"

height="400">

<jsp:fallback>

<p>Unable to use Java Plugin</p>

</jsp:fallback>

</jsp:plugin>