Delegate compression to servlet container

[basil]

Part of a series of three PRs:

• Delegate compression to servlet container jenkins#9379
• Delegate compression to servlet container #557
• Delegate compression to servlet container winstone#390

The primary description of this change is written in jenkinsci/jenkins#9379.

Testing done

See jenkinsci/jenkins#9379.

Fixes #130
Fixes #265

[basil]

The GitHub diff page makes this unreviewable, as it is a rename of CompressionFilter with some simplifications. Here is the actual diff. Please only comment on the changed portions, not the original code which I am not changing.

--- core/src/main/java/org/kohsuke/stapler/compression/CompressionFilter.java	2024-06-12 12:42:12.076182060 -0700
+++ /tmp/UncaughtExceptionFilter.java	2024-06-12 12:42:11.216183675 -0700
@@ -1,4 +1,4 @@
-package org.kohsuke.stapler.compression;
+package org.kohsuke.stapler;
 
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import java.io.IOException;
@@ -12,28 +12,7 @@
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
-/**
- * Pimps up {@link HttpServletResponse} so that it understands "Content-Encoding: gzip" and compress the response.
- *
- * <p>
- * When exceptions are processed within web applications, different unrelated parts of the webapp can end up calling
- * {@link HttpServletResponse#getOutputStream()}. This fundamentally doesn't work with the notion that the application
- * needs to process "Content-Encoding:gzip" on its own. Such app has to maintain a GZIP output stream on its own,
- * since {@link HttpServletResponse} doesn't know that its output is written through a compressed stream.
- *
- * <p>
- * Another place this break-down can be seen is when a servlet throws an exception that the container handles.
- * It tries to render an error page, but of course it wouldn't know that "Content-Encoding:gzip" is set, so it
- * will fail to write in the correct format.
- *
- * <p>
- * The only way to properly fix this is to make {@link HttpServletResponse} smart enough that it returns
- * the compression-transparent stream from {@link HttpServletResponse#getOutputStream()} (and it would also
- * have to process the exception thrown from the app.) This filter does exactly that.
- *
- * @author Kohsuke Kawaguchi
- */
-public class CompressionFilter implements Filter {
+public class UncaughtExceptionFilter implements Filter {
     private ServletContext context;
 
     @Override
@@ -42,34 +21,18 @@
     }
 
     @Override
-    public void doFilter(ServletRequest _req, ServletResponse _rsp, FilterChain filterChain)
+    public void doFilter(ServletRequest req, ServletResponse rsp, FilterChain filterChain)
             throws IOException, ServletException {
-        Object old1 = swapAttribute(_req, CompressionFilter.class, true);
-
-        CompressionServletResponse rsp = new CompressionServletResponse((HttpServletResponse) _rsp);
-        Object old2 = swapAttribute(_req, CompressionServletResponse.class, rsp);
-
         try {
-            filterChain.doFilter(_req, rsp);
+            filterChain.doFilter(req, rsp);
         } catch (IOException | Error | RuntimeException | ServletException e) {
             if (DISABLED) {
                 throw e;
             }
-            reportException(e, (HttpServletRequest) _req, rsp);
-        } finally {
-            rsp.close();
-
-            _req.setAttribute(CompressionFilter.class.getName(), old1);
-            _req.setAttribute(CompressionServletResponse.class.getName(), old2);
+            reportException(e, (HttpServletRequest) req, (HttpServletResponse) rsp);
         }
     }
 
-    private Object swapAttribute(ServletRequest req, Class<?> key, Object value) {
-        Object old = req.getAttribute(key.getName());
-        req.setAttribute(key.getName(), value);
-        return old;
-    }
-
     private void reportException(Throwable e, HttpServletRequest req, HttpServletResponse rsp)
             throws IOException, ServletException {
         getUncaughtExceptionHandler(context).reportException(e, context, req, rsp);
@@ -92,33 +55,8 @@
     }
 
     /**
-     * Is this request already wrapped into {@link CompressionFilter}?
-     */
-    public static boolean has(ServletRequest req) {
-        return req.getAttribute(CompressionServletResponse.class.getName()) != null;
-    }
-
-    /**
-     * Is this request already wrapped into {@link CompressionFilter},
-     * activate that, so that {@link ServletResponse#getOutputStream()} will return
-     * a stream that automatically handles compression.
-     */
-    public static boolean activate(ServletRequest req) throws IOException {
-        CompressionServletResponse rsp =
-                (CompressionServletResponse) req.getAttribute(CompressionServletResponse.class.getName());
-        if (rsp != null) {
-            rsp.activate();
-            return true;
-        } else {
-            return false;
-        }
-    }
-
-    /**
      * Disables the effect of {@link #setUncaughtExceptionHandler}, letting all errors be rethrown.
-     * Despite its name, this flag does <strong>not</strong> disable {@link CompressionFilter} itself!
-     * Rather use {@code DefaultScriptInvoker.COMPRESS_BY_DEFAULT}.
      */
     @SuppressFBWarnings(value = "MS_SHOULD_BE_FINAL", justification = "Legacy switch.")
-    public static boolean DISABLED = Boolean.getBoolean(CompressionFilter.class.getName() + ".disabled");
+    public static boolean DISABLED = Boolean.getBoolean(UncaughtExceptionFilter.class.getName() + ".disabled");
 }