Why Use Try-With-Resources Without Catch or Finally in Java?

Question

What is the purpose of using Try-With-Resources in Java without Catch or Finally blocks?

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    try (PrintWriter out = response.getWriter()) {
        /* Output HTML content */
        out.println("<!DOCTYPE html>");
        out.println("<html>");
        out.println("<head>");
        out.println("<title>Servlet tryse</title>");            
        out.println("</head>");
        out.println("<body>");
        out.println("<h1>Servlet tryse at " + request.getContextPath() + "</h1>");
        out.println("</body>");
        out.println("</html>");
    }
}

Answer

In Java, the try-with-resources statement is a powerful feature that simplifies resource management by automatically closing resources, such as files or network connections, when done. This mechanism alleviates the need for explicit catch or finally blocks especially in cases where exceptions are not expected to be handled directly, nor are they critical to operation success.

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    try (PrintWriter out = response.getWriter()) {
        // Generate HTML response
        out.println("<!DOCTYPE html>");
        out.println("<html>");
        out.println("<head>");
        out.println("<title>Servlet tryse</title>");
        out.println("</head>");
        out.println("<body>");
        out.println("<h1>Servlet tryse at " + request.getContextPath() + "</h1>");
        out.println("</body>");
        out.println("</html>");
    }
}

Causes

Java's try-with-resources automatically manages the lifecycle of resources, hence catch or finally may not be necessary if no further actions are required after resource closure.
In this specific HTTP servlet example, closing the PrintWriter is sufficient since there are no critical exceptions to handle during the writing process.

Solutions

Use try-with-resources when managing I/O streams or other closeable resources to prevent potential resource leaks without cluttering code with unnecessary error handling.
Rely on the natural exception propagation in the method signature to handle exceptions effectively in higher layers of your application.

Common Mistakes

Mistake: Ignoring exception handling altogether.

Solution: Consider documenting expected behaviors and outcomes of the method, or handle exceptions at a higher level.

Mistake: Assuming all resources require catch or finally blocks.

Solution: Understand the purpose of try-with-resources and its exception handling mechanisms.

Helpers

Java try-with-resources
Printing in servlets
Servlet exception handling
Java resource management
Try-with-resources advantages