Developing ColdFusion MX Applications with CFML
Integrating J2EE and Java Elements in CFML Applications

Interoperating with JSP pages and servlets

ColdFusion pages and JSP pages can interoperate in several ways:

• ColdFusion pages can invoke JSP pages and servlets.
• JSP pages can invoke ColdFusion pages.
• ColdFusion pages, JSP pages, and servlets can share data in three scopes.

The following sections show how you can use these techniques.

Integrating JSP and servlets in a ColdFusion application

You can integrate JSP pages and servlets in your ColdFusion application. For example, you can write some application pages in JSP and write others in CFML. ColdFusion pages can access JSP pages by using the JSP include and forward methods to call the page. As with any web application, you can use href links in ColdFusion pages to open JSP pages.

The ability to use JSP lets you incorporate legacy JSP pages in your ColdFusion application, or conversely, use CFML to expand an existing JSP application using ColdFusion pages.

If you have a JSP page that must call a ColdFusion page, you also use a jsp:forward or jsp:include tag to call the ColdFusion page. For an example of calling a ColdFusion page from a JSP page, see "Calling a JSP page from a ColdFusion page".

Accessing a JSP page or servlet from a ColdFusion page

To access a JSP page or servlet from a ColdFusion page, you use the getPageContext function with the forward or the include method. For example, to include a JSP "Hello World" page in your ColdFusion application, use the following line:

GetPageContext().include("hello.jsp");

To pass parameters to the JSP page, include the parameters in the page URL.

For example, you might want to integrate an existing JSP customer response component into a new ColdFusion order processing application. The order processing application provides the order number, total cost, and expected shipping date, and the customer response component sends the response to the e-mail address on file for the particular customer number. The ColdFusion application might use the following CFScript code to call the response JSP page:

urlParams = "UID=#order.uid#&cost=#order.total#&orderNo=#order.orderNo#
&shipDate=#order.shipDateNo#"

getPageContext().forward(URLEncodedFormat("/responsegen/responsegen.jsp
?#urlParams#"));

To access a servlet that exposes the same functionality, you use the same code, although the URL would change. For example, to run a servlet called HelloWorldServlet, you put the servlet .java or .class file in the serverroot/WEB-INF/classes directory and refer to the servlet with the URL /servlet/HelloWorldServlet.

Sharing data between ColdFusion pages and JSP pages or servlets

If an application includes ColdFusion pages and JSP pages or servlets, they can share data in the Request, Session and Application scopes. The following table lists the ways that you can access JSP pages with which you want to share the scope data:

Scope	Can share data using
Request	forward, include
Session	href, cfhttp, forward, include
Application	href, cfhttp, forward, include

Note:   When you share data between ColdFusion pages and JSP pages, you must be careful about data type conversion issues. For more information, see "Java and ColdFusion Data Type Conversions".

To share session variables, you must specify J2EE session management in the ColdFusion Administrator. For more information on configuring and using J2EE Session scope management, see "ColdFusion and J2EE session management," in Chapter 15.

For example, you could put the customer order structure used in the previous example in the Session scope. Then, you would not have to pass the order values as a set of parameters. Instead, the JSP pages could access the Session scope variables directly, and the ColdFusion page would only require a line like the following to call the JSP page:

getPageContext().forward(URLEncodedFormat("/responsegen/responsegen.jsp"));

For examples of using the Request, Session, and Application scopes to share data between ColdFusion pages and JSP pages, including samples of the appropriate JSP code, see the following section, "Examples: using JSP with CFML" .

Accessing ColdFusion application and session variables in JSP pages

ColdFusion runs as a J2EE application on the J2EE application server. The J2EE application ServletContext is a data structure that stores objects as attributes. A ColdFusion Application scope is represented as an attribute named by the Application scope name. The attribute contains the scope values as a hash table. Therefore, you access ColdFusion Application scope variable in a JSP page or servlet using the following format:

((Map)application.getAttribute("CFApplicationName"))).get("appVarName")

Similarly, the ColdFusion Session scope is a structure within the J2EE session. Because ColdFusion identifies sessions by the application name. the session structure is contained in an attribute of the J2EE session that is identified by the application name. Therefore, you access ColdFusion session variables as follows:

((Map)(session.getAttribute("CFApplicationName"))).get("sessionVarName")

Unnamed ColdFusion Application and Session scopes

If you do not specify an application name in the ColdFusion cfapplication tag, the application is unnamed. ColdFusion supports only a single unnamed application, so if multiple cfapplication tags do not specify an application name, all pages affected by the tags share the single unnamed application Scope. This scope maps directly to the J2EE application scope. Similarly, all sessions of unnamed applications correspond directly to the J2EE application server's session scope.

You access an Application scope variable from a ColdFusion unnamed application in a JSP page using the following format:

application.getAttribute("applicationVariableName")

You access Session scope variables in a ColdFusion unnamed application as follows:

session.getAttribute("sessionVariableName")

Note:   When you use application and session variables for the unnamed ColdFusion application in JSP pages and servlets, the variable names must be case-correct. That is, the characters in the variable name must have the same case as you used when you created the variable in ColdFusion. You do not have to use case-correct application and session variable names for named ColdFusion applications.

Examples: using JSP with CFML

The following simple examples show how you can integrate JSP pages, servlets, and ColdFusion pages. They also show how you can use the Request, Application, and Session scopes to share data between ColdFusion pages, JSP pages, and servlets.

Calling a JSP page from a ColdFusion page

The following page sets Request, Session, and application variables and calls a JSP page, passing it a name parameter:

<cfapplication name="myApp" sessionmanagement="yes">

<cfscript>
Request.myVariable = "This";
Session.myVariable = "is a";
Application.myVariable = "test.";
GetPageContext().include("hello.jsp?name=Bobby");
</cfscript>

Reviewing the code

The following table describes the CFML code and its function:

Code	Description
<cfapplication name="myApp" sessionmanagement="yes">	Specifies the application name as myApp and enables session management. In most applications, this tag is in the Application.cfm page.
<cfscript> Request.myVariable = "This"; Session.myVariable = "is a"; Application.myVariable = "test.";	Sets ColdFusion Request, Session, and Application, scope variables. Uses the same name, myVariable, for each variable.
GetPageContext().include ("hello.jsp?name=Bobby"); </cfscript>	Uses the getPageContext function to get the current servlet page context for the ColdFusion page. Uses the include method of the page context object to call the hello.jsp page. Passes the name parameter in the URL.

The hello.jsp page is called by the CFML. It displays the Name parameter in a header and the three variables in the remainder of the body.

<%@page import="java.util.*" %>

<h2>Hello <%= request.getParameter("Name")%>!</h2>

<br>Request.myVariable: <%= request.getAttribute("myvariable")%>
<br>session.myVariable: <%= ((Map)(session.getAttribute("myApp")))
.get("myVariable")%>
<br>Application.myVariable: <%= ((Map)(application.getAttribute("myApp")))
.get("myVariable")%>

Reviewing the code

The following table describes the JSP code and its function:

Code	Description
<%@page import="java.util.*" %>	Imports the java.util package. This contains methods required in the JSP page.
<h2>Hello <%= request.getParameter ("name")%>!</h2>	Displays the name passed as a URL parameter from the ColdFusion page. The parameter name is case-sensitive,
<br>request.myVariable: <%= request. getAttribute("myvariable")%>	Uses the getAttribute method of the JSP request object to displays the value of the Request scope variable myVariable.
<br>session.myVariable: <%= ((Map)(session.getAttribute("myApp"))). get("myVariable")%>	Uses the getAttribute method of the JSP session object to get the myApp object (the Application scope). Casts this to a Java Map object and uses the get method to obtain the myVariable value for display.
<br>Application.myVariable: <%= ((Map)(application.getAttribute("myApp"))) .get("myVariable")%>	Uses the getAttribute method of the JSP myApp application object to obtain the value of myVariable in the Application scope.

Calling a ColdFusion page from a JSP page

The following JSP page sets Request, Session, and application variables and calls a ColdFusion page, passing it a name parameter:

<%@page import="java.util.*" %>

<% request.setAttribute("myvariable", "This");%>
<% ((Map)session.getAttribute("myApp")).put("myVariable", "is a");%> 
<% application.setAttribute("myApp.myvariable", "test.");%>

<jsp:include page="hello.cfm"> 
   <jsp:param name="name" value="Robert" />
</jsp:include>

Reviewing the code

The following table describes the JSP code and its function:

Code	Description
<%@page import="java.util.*" %>	Imports the java.util package. This contains methods required in the JSP page.
<% request.setAttribute("myvariable", "This");%>	Uses the setAttribute method of the JSP request object to set the value of the Request scope variable myVariable.
<% ((Map)session.getAttribute("myApp")) .put("myVariable", "is a");%>	Uses the getAttribute method of the JSP session object to get the myApp object (the Application scope). Casts this to a Java Map object and uses the set method to set the myVariable value.
<% application.setAttribute ("myApp.myvariable", "test.");%>	Uses the setAttribute method of the JSP application object to set the value of myVariable in the myApp application scope.
<jsp:include page="hello.cfm"> <jsp:param name="name" value="Robert" /> </jsp:include>	Sets the name parameter to Robert and calls the ColdFusion page hello.cfm.

The following hello.cfm page is called by the JSP page. It displays the Name parameter in a heading and the three variables in the remainder of the body.

<cfapplication name="myApp" sessionmanagement="yes">

<cfoutput>
<h2>Hello #URL.name#!</h2>
Request.myVariable: #Request.myVariable#<br>
Session.myVariable: #Session.myVariable#<br>
Application.myVariable: #Application.myVariable#<br>

</cfoutput>

Reviewing the code

The following table describes the CFML code and its function:

Code	Description
<cfapplication name="myApp" sessionmanagement="yes">	Specifies the application name as myApp and enables session management. In most applications, this tag is in the Application.cfm page.
<h2>Hello #URL.name#!</h2>	Displays the name passed using the jsp:param tag on the JSP page. The parameter name is not case-sensitive.
Request.myVariable: #Request.myVariable#<br> Session.myVariable: #Session.myVariable#<br> Application.myVariable: #Application.myVariable#<br>	Displays the Request.myVariable, Session. myVariable, and Application.myVariable values.

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