Java. Lang. illegalstateexception: cannot forward after response has been committed

Error message:

Severe: servlet. Service () for servlet showbaby threw exception
Java. Lang. illegalstateexception: cannot forward after response has been committed
At org. Apache. Catalina. Core. applicationdispatcher. doforward (applicationdispatcher. Java: 312)
At org. Apache. Catalina. Core. applicationdispatcher. Forward (applicationdispatcher. Java: 302)
At com. shyy. JB. epet. servlet. showbabyservlet. doget (showbabyservlet. Java: 37)
At javax. servlet. http. httpservlet. Service (httpservlet. Java: 690)
At javax. servlet. http. httpservlet. Service (httpservlet. Java: 803)
At org. Apache. Catalina. Core. applicationfilterchain. internaldofilter (applicationfilterchain. Java: 290)
At org. Apache. Catalina. Core. applicationfilterchain. dofilter (applicationfilterchain. Java: 206)
At com. shyy. JB. epet. Filter. setcharacterencodingfilter. dofilter (setcharacterencodingfilter. Java: 32)
At org. Apache. Catalina. Core. applicationfilterchain. internaldofilter (applicationfilterchain. Java: 235)
At org. Apache. Catalina. Core. applicationfilterchain. dofilter (applicationfilterchain. Java: 206)
At org. Apache. Catalina. Core. standardwrappervalve. Invoke (standardwrappervalve. Java: 233)
At org. Apache. Catalina. Core. standardcontextvalve. Invoke (standardcontextvalve. Java: 175)
At org. Apache. Catalina. Core. standardhostvalve. Invoke (standardhostvalve. Java: 128)
At org. Apache. Catalina. Valves. errorreportvalve. Invoke (errorreportvalve. Java: 102)
At org. Apache. Catalina. Core. standardenginevalve. Invoke (standardenginevalve. Java: 109)
At org. Apache. Catalina. connector. coyoteadapter. Service (coyoteadapter. Java: 286)
At org. Apache. Coyote. http11.http11processor. Process (http11processor. Java: 844)
At org. Apache. Coyote. http11.http11protocol $ http11connectionhandler. Process (http11protocol. Java: 583)
At org.apache.tomcat.util.net. jioendpoint $ worker. Run (jioendpoint. Java: 447)
At java. Lang. thread. Run (unknown source)

Source code:

Public void doget (httpservletrequest request, httpservletresponse response)
Throws servletexception, ioexception {
String id = request. getparameter ("ID ");
If (null = ID | ID. Equals ("")){
Request. setattribute ("error", "no pet number specified! ");
// Response. sendredirect ("/WEB-INF/JSP/error. jsp"); // redirection, changing the address bar address on the browser side
Request. getrequestdispatcher ("/WEB-INF/JSP/error. jsp"). Forward (request, response); // forward, jump on the server side, address unchanged
}
Integer petid = integer. valueof (ID );

Petinfobiz biz = new petinfobizimpl ();
Petinfo = biz. Load (petid); // load the pet information by ID
If (null = petinfo ){
Request. setattribute ("error", "no pet record specified! "); // A pet without this ID will jump to the error page
Request. getrequestdispatcher ("/WEB-INF/JSP/error. jsp"). Forward (request, response );
}
Request. setattribute ("item", petinfo );
Request. getrequestdispatcher ("/WEB-INF/JSP/PET/petinfo. jsp"). Forward (request, response );
}

This is a simple servlet. What I typed in the address bar is:

Http: // localhost: 8080/epet/showbaby. do? Id = 4

The database does not have the ID 4. In theory, the error page should be redirected, but no.

Error cause:

If {......} Else {......} This is a logical judgment statement. It only has if {} but does not have else {}. Sometimes it continues to execute external statements, causing errors.

Solution:

If (null = petinfo ){
Request. setattribute ("error", "no pet record specified! "); // A pet without this ID will jump to the error page
Request. getrequestdispatcher ("/WEB-INF/JSP/error. jsp"). Forward (request, response );
}Else {
Request. setattribute ("item", petinfo );
Request. getrequestdispatcher ("/WEB-INF/JSP/PET/petinfo. jsp"). Forward (request, response );

}
}

Add else {}

If (null = petinfo ){
Request. setattribute ("error", "no pet record specified! "); // A pet without this ID will jump to the error page
Request. getrequestdispatcher ("/WEB-INF/JSP/error. jsp"). Forward (request, response );

Return;
}
Request. setattribute ("item", petinfo );
Request. getrequestdispatcher ("/WEB-INF/JSP/PET/petinfo. jsp"). Forward (request, response );
}

Add a return after if, so that the statement outside if is not executed. OK. Solve the problem.