Tomcat: Java Servlet responses weird characters when called from JavaScript

0
votes

In TestAjax.java（Location：webapps/servlets/，is compiled）:

public void doGet(HttpServletRequest request,
                      HttpServletResponse response)
        throws IOException, ServletException
{ 
        String data = "Hello World";
        response.setContentType("text/plain");
        response.setCharacterEncoding("UTF-8");
        response.getWriter().write(data);
}

In HTML(JavaScript)：

function showHelloWorld(inputForm) {
                var xhr = new XMLHttpRequest();
                    xhr.onreadystatechange = function() {
                        if (xhr.readyState == 4) {
                            var data = xhr.responseText;
                            alert(data);
                        }
                    }
                 xhr.open('GET', '../../examples/servlets/TestAjax.class', true);
                 xhr.send(null);
}

In web.xml:

<servlet> 
<servlet-name>TestAjax</servlet-name> 
<display-name>TestAjax</display-name> 
<servlet-class>TestAjax</servlet-class> 
</servlet>  
<servlet-mapping> 
<servlet-name>TestAjax</servlet-name> 
<url-pattern>/servlet/TestAjax</url-pattern> 
</servlet-mapping>

Symptom:

When showHelloWorld() is executed, the alert box shows this:

����2,

!()VCodeLineNumberTabledoGetR(Ljavax/servlet/http/HttpServletRequest;Ljavax/servlet/http/HttpServletResponse;)V Exceptions"# SourceFile TestAjax.java*Hello World* text/plain$%&UTF-8'&()*+&TestAjaxjavax/servlet/http/HttpServletjava/io/IOExceptionjavax/servlet/ServletException&javax/servlet/http/HttpServletResponsesetContentType(Ljava/lang/String;)VsetCharacterEncoding getWriter()Ljava/io/PrintWriter;java/io/PrintWriterwrite!

*�� FN,�,�,�-��?@ABC

Note there is "Hello World" in it, but the correct response should only have "Hello World", there shouldn't be all these craps in the response.

I've checked the code and deployment a million times, still found no clue.

Please shed some light on this problem, I would appreciate it very much!

1
tomcatservlets

1 Answers

0
votes

You are trying to load a compiled Java class client side, which is normal you get strange characeters. What you probably want is to call the servlet path :

xhr.open('GET', '<%=request.getContextPath()%>/servlet/TestAjax', true);

Remember the <url-pattern>/servlet/TestAjax</url-pattern>, this is the external mapping to your Servlet Class. The Application container forward requests to it by this path.