What is jsp:setProperty, jsp:getProperty, standard and jsp:plugin action?

jsp:setProperty action

You use jsp:setProperty to give values to properties of beans that have been referenced earlier. You can do this in two contexts. First, you can use jsp:setProperty after, but outside of, a jsp:useBean element, as below:

<jsp:useBean id="myName" ... />
...
<jsp:setProperty name="myName" property="myProperty" ... />

In this case, the jsp:setProperty is executed regardless of whether a new bean was instantiated or an existing bean was found.

A second context in which jsp:setProperty can appear is inside the body of a jsp:useBean element, as below:

<jsp:useBean id="myName" ... >
...
<jsp:setProperty name="myName"
property="someProperty" ... />
</jsp:useBean>

Here, the jsp:setProperty is executed only if a new object was instantiated, not if an existing one was found.

jsp:getProperty action

The <jsp:getProperty> action is used to access the properties of a bean that was set using the <jsp:getProperty> action. The container converts the property to a String as follows:

• If it is an object, it uses the toString() method to convert it to a String.

• If it is a primitive, it converts it directly to a String using the valueOf() method of the corresponding Wrapper class.

• The syntax of the <jsp:getProperty> method is: <jsp:getProperty name="Name" property="Property" />

Here, name is the id of the bean from which the property was set. The property attribute is the property to get. A user must create or locate a bean using the <jsp:useBean> action before using the <jsp:getProperty> action.

<jsp:param> standard action

The <jsp:param> standard action is used with <jsp:include> or <jsp:forward> to pass parameter names and values to the target resource. The syntax of the <jsp:param> standard action is as follows: <jsp:param name="paramName" value="paramValue"/>

jsp:plugin action

This action lets you insert the browser-specific OBJECT or EMBED element needed to specify that the browser run an applet using the Java plugin.

What is the difference between include directive and include action?

JSP: What are the JSP standard actions?

The JSP standard actions affect the overall runtime behavior of a JSP page and also the response sent back to the client.

• They can be used to include a file at the request time, to find or instantiate a JavaBean, to forward a request to a new page, to generate a browser-specific code, etc.

• Ex: include, forward, useBean,etc. object

The standard actions available in JSP are as follows:

• <jsp:include>: It includes a response from a servlet or a JSP page into the current page. It differs from an include directive in that it includes a resource at request processing time, whereas the include directive includes a resource at translation time.

• <jsp:forward>: It forwards a response from a servlet or a JSP page to another page.

• <jsp:useBean>: It makes a JavaBean available to a page and instantiates the bean.

• <jsp:setProperty>: It sets the properties for a JavaBean.

• <jsp:getProperty>: It gets the value of a property from a JavaBean component and adds it to the response.

• <jsp:param>: It is used in conjunction with <jsp:forward>;, <jsp:, or plugin>; to add a parameter to a request. These parameters are provided using the name-value pairs.

• <jsp:plugin>: It is used to include a Java applet or a JavaBean in the current JSP page.

<jsp:useBean> standard action

The <jsp:useBean> standard action is used to locate an existing JavaBean or to create a JavaBean if it does not exist. It has attributes to identify the object instance, to specify the lifetime of the bean, and to specify the fully qualified classpath and type.

The scopes available in <jsp:useBean> are as follows:

• page scope:: It specifies that the object will be available for the entire JSP page but not outside the page.

• request scope: It specifies that the object will be associated with a particular request and exist as long as the request exists.

• application scope: It specifies that the object will be available throughout the entire Web application but not outside the application.

• session scope: It specifies that the object will be available throughout the session with a particular client.

<jsp:forward> standard action

The <jsp:forward> standard action forwards a response from a servlet or a JSP page to another page.

• The execution of the current page is stopped and control is transferred to the forwarded page.

• The syntax of the <jsp:forward> standard action is : <jsp:forward page="/targetPage" /> Here, targetPage can be a JSP page, an HTML page, or a servlet within the same context.

• If anything is written to the output stream that is not buffered before <jsp:forward>, an IllegalStateException will be thrown.

Note : Whenever we intend to use <jsp:forward> or <jsp:include> in a page, buffering should be enabled. By default buffer is enabled.

<jsp:include> standard action

The <jsp:include> standard action enables the current JSP page to include a static or a dynamic resource at runtime. In contrast to the include directive, the include action is used for resources that change frequently. The resource to be included must be in the same context.The syntax of the <jsp:include> standard action is as follows:

<jsp:include page="targetPage" flush="true"/> Here, targetPage is the page to be included in the current JSP.

JSP: What is the include directive?

There are thirteen attributes defined for a page directive of which the important attributes are as follows:

• The include directive is used to statically insert the contents of a resource into the current JSP.

• This enables a user to reuse the code without duplicating it, and includes the contents of the specified file at the translation time.

• The syntax of the include directive is as follows: <%@ include file = "FileName" %>

• This directive has only one attribute called file that specifies the name of the file to be included.

JSP: What is page directive?

A page directive is to inform the JSP engine about the headers or facilities that page should get from the environment.

• Typically, the page directive is found at the top of almost all of our JSP pages.

• There can be any number of page directives within a JSP page (although the attribute – value pair must be unique).

• The syntax of the include directive is: <%@ page attribute="value">

• Example :<%@ include file="header.jsp" %>

There are thirteen attributes defined for a page directive of which the important attributes are as follows:

• import: It specifies the packages that are to be imported.

• session: It specifies whether a session data is available to the JSP page.

• contentType: It allows a user to set the content-type for a page.

• isELIgnored: It specifies whether the EL expressions are ignored when a JSP is translated to a servlet.

JSP: What are JSP directives?

JSP directives are messages for the JSP engine. i.e., JSP directives serve as a message from a JSP page to the JSP container and control the processing of the entire page.

• They are used to set global values such as a class declaration, method implementation, output content type, etc.

• They do not produce any output to the client.

• Directives are always enclosed within <%@ ….. %> tag.

• Ex: page directive, include directive, etc.

JSP: What are the different types of JSP tags?

JSP tags are: