Servlets are components in Java web development, responsible for processing HTTP requests and generating responses. In this context, exceptions are used to handle and manage unexpected errors or exceptional conditions that may occur during the execution of a servlet.
Catching exceptions within the servlet allows us to convert them into meaningful, user-friendly messages. Otherwise, failing to catch exceptions will propagate them to the servlet container, where the default error-handling mechanism may impact the overall security and stability of the server.
Possible security problems are:
Unfortunately, servlet method signatures do not force developers to handle IOException
and ServletException
:
public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { }
To prevent this risk, this rule enforces all exceptions to be caught within the "do*" methods of servlet classes.
Surround all method calls that may throw an exception with a try/catch
block.
In the following example, the getByName
method may throw an UnknownHostException
.
public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { InetAddress addr = InetAddress.getByName(request.getRemoteAddr()); // Noncompliant //... }
public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { try { InetAddress addr = InetAddress.getByName(request.getRemoteAddr()); //... } catch (UnknownHostException ex) { // Compliant //... } }