login

Subscribe to JSP Tutorial websiteRSS Feed
 » JSP Tutorial » JSP Standard Actions

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:

<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:

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

By using the jsp:useBean action, you create an new object with the object name objectName 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 expression.

 

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

jsp:plugin Action

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

</body>
</html>