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At times, your system may issue a request dispatcher message indicating that another servlet should be called. This error can have various reasons. You can call this servlet programmatically from another servlet in two ways. To embody the output of another servlet, use the include () method of the RequestDispatcher computer program. This method calls the servlet for its URI and waits for it to return before continuing with the communication.
public interface RequestDispatcher. Defines the type of object that frequently receives requests from the client and dispatches them to almost any resource (such as a servlet, HTML file, or JSP file) on our server.
I am using Net Beans 7.1 and am creating a JSP statement with two servlet files.like:
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index.jsp ---> servlet1.java ---> servlet2.java
You can call a servlet by accessing it directly from a web page using a URL, or you can call it programmatically from a normally working servlet.
I enter some values into index.jsp file and send servlet1.java .
Index.jsp
Servlet1.java
@Overrideprotected empty doPost (HttpServletRequest, HttpServletResponse response) results in ServletException, IOException. outside ..................... ..................... ..................... servlet2 ob = new servlet2 (); ob.doPost (request, response); ..................... ..................... .....................
1 answer. You can use URLConnection to call all of your servlets that are in another application on the same server or on a different server. To call a servlet, you must enter the URL of that servlet, pass the request parameter to the servlet, and thus , read the response from this servlet.
A discussion of information servlets in a particular Java web application turns out to be a collaboration of servlets. This sharing means that you can use method calls to send information from one servlet to another.
What are the core capabilities of Java for servlet collaboration?
Servlet provides two APIs, namely:
- javax.servlet.RequestDispatcher
- javax.servlet.http.HttpServletResponse
These two interfaces group together the methods responsible for achieving the goal of communicating with respect to servlets.
The RequestDispatcher interface provides the ability to redirect a client’s request to another web resource, which can be a specific HTML page, another servlet, or a JSP helper. It offers the following two empty methods:
- a public forward is generated (ServletRequest, ServletResponse), ServletException, java.io.IOException:
The forward () method is used to send a client request to a much larger resource file (html, jsp servlet, etc.) etc.). When this method is called, control is transferred to the additional callable resource. On the other hand, the include () method allows you to include the contents of a file contact in the file being called. After calling this method, control of the calling resource has been taken, but our processed output is included in the new called resource.
The following diagram explains how it works:
- public void include (ServletRequest ServletResponse request, response) issuesServletException, java.io.IOException:
The include () pattern is used to include the elements of the calling resource in the called resource. Calling this subroutine leaves the control containing the calling resource. It simply adds the processed output of the telephone dialing resource to the callee.
The following diagram explains how it works:
- Example Using RequestDispatcher to Coexist Servlets
The following example explains how to use the RequestDispatcher interface to achieve coexistence of servlets:
index.html
- Login.java
- Welcome.java
- web.xml
- index.html
- If the personal details match:
- If the password does not match:
- The httpservletresponse interface is responsible for handling HTTP responses. The servlet will use the following method to achieve collaboration:
public void sendRedirect (String URL) throws an IOException;
- This method allows you to redirect the response to another resource, which unfortunately could be a servlet, jsp, or even an HTML file. The accepted fact is the url that It can be either absolute or comparable. It works with less visible client apps and a browser url cooler to make a request.
- In the following illustration of an embedded web application that generates a servlet, text written in a text box on a page is passed to the servlet. The servlet then forwards it along the path to Google, which then generates search results based on the written text.
index.html
- web.xml
- index.html
- Search Result
What is the difference between the forward () mode of RequestDiispatcher and the sendRedirect () from HttpServletResponse?
- While both methods seem to do the same thing on a regular basis, there are still differences between them, which could be as follows:
| forward () | sendRedirect () |
| Works on the main server side < / td> | Runs on the site visitor’s page |
| Sends the same request with response objects to another resource. | It always sends a new request |
| This only works inside the server. | It can be used internally and externally faith. |
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RequestDispatcher rd = request.getRequestDispatcher (“servlet2”);// servlet2 is usually the URL pattern for the second servlet.rd.forward (request, response); // Method can be included or passed.
