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How to add JSR-045 SMAP information to Java stack stack at runtime?

When working with JSP or with other languages ​​that have been converted to Java source code (or stubs), an SMAP file is often created, which can later be embedded in a class file for debuggers to show the best stack traces (or, in the case of Jasper, it is automatically injected )

There is some old JVM (or RFE) bug to add support for including SMAP information in the stack trace, but due to inactivity, the Sun / Oracle guys prefer each post processor to keep track of its stack.

So here is my question: how to do this? Are there libraries that do the hard work for you, or do you need to implement everything yourself?

I have already found a good place where I have access to both the exception object and the class loader loading classes with SMAP support. Now i have to

  • stack trace iteration
  • Check every entry if I can find a class
  • Analyze the class with e. Mr. ASM to extract SMAP information
  • Write a SMAP parser that analyzes the return line mapping and file names from the SMAP information.
  • Replace the stack trace element with a new one based on the mapping (or, conversely, add a new one? Which is better?)
  • Download some information so I don’t have to repeat the same material if after a few seconds the exact (or similar) stack trace appears again.

And since this seems like a tedious and error-prone task, I hope someone has already done this, and I just need to add the library to my dependencies and call the makeStacktraceFancy method for my exceptions to make stacktraces fancy before I write them.

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2 answers

Since no one seems to be aware of the existing solution, I rolled my own quick and dirty.

It does not support all SMAP functions (it analyzes only the first layer and ignores the vendor sections and default status information), but this is enough for my needs.

Since the code to extract the SMAP attribute from the class is only about 50 lines, I decided to redefine it instead of adding ASM as a dependency. The code for use with ASM is in the comments.

Since it has been tested very little (in several test cases), I will edit the message if I encounter serious errors.

Code below:

 /* * SMAPSourceDebugExtension.java - Parse source debug extensions and * enhance stack traces. * * Copyright (c) 2012 Michael Schierl * * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * - Redistributions of source code must retain the above copyright notice, * this list of conditions and the following disclaimer. * * - Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * - Neither name of the copyright holders nor the names of its * contributors may be used to endorse or promote products derived from * this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND THE CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT * HOLDERS OR THE CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR * TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ package smap; import java.io.*; import java.util.*; import java.util.regex.*; /** * Utility class to parse Source Debug Extensions and enhance stack traces. * * Note that only the first stratum is parsed and used. * * @author Michael Schierl */ public class SMAPSourceDebugExtension { /** * Enhance a stack trace with information from source debug extensions. * * @param t * Throwable whose stack trace should be enhanced * @param cl * Class loader to load source debug extensions from * @param keepOriginalFrames * Whether to keep the original frames referring to Java source * or drop them * @param packageNames * Names of packages that should be scanned for source debug * extensions, or empty to scan all packages * @throws IOException * if an I/O error occurs */ public static void enhanceStackTrace(Throwable t, ClassLoader cl, boolean keepOriginalFrames, String... packageNames) throws IOException { enhanceStackTrace(t, new HashMap<String, SMAPSourceDebugExtension>(), cl, keepOriginalFrames, packageNames); } /** * Enhance a stack trace with information from source debug extensions. * Provide a custom cache of already resolved and parsed source debug * extensions, to avoid parsing them for every new exception. * * @param t * Throwable whose stack trace should be enhanced * @param cache * Cache to be used and filled * @param cl * Class loader to load source debug extensions from * @param keepOriginalFrames * Whether to keep the original frames referring to Java source * or drop them * @param packageNames * Names of packages that should be scanned for source debug * extensions, or empty to scan all packages * @throws IOException * if an I/O error occurs */ public static void enhanceStackTrace(Throwable t, Map<String, SMAPSourceDebugExtension> cache, ClassLoader cl, boolean keepOriginalFrames, String... packageNames) throws IOException { StackTraceElement[] elements = t.getStackTrace(); List<StackTraceElement> newElements = null; for (int i = 0; i < elements.length; i++) { String className = elements[i].getClassName(); SMAPSourceDebugExtension smap = cache.get(className); if (smap == null) { boolean found = false; for (String packageName : packageNames) { if (className.startsWith(packageName + ".")) { found = true; break; } } if (found || packageNames.length == 0) { InputStream in = cl.getResourceAsStream(className.replace('.', '/') + ".class"); if (in != null) { String value = extractSourceDebugExtension(in); in.close(); if (value != null) { value = value.replaceAll("\r\n?", "\n"); if (value.startsWith("SMAP\n")) { smap = new SMAPSourceDebugExtension(value); cache.put(className, smap); } } } } } StackTraceElement newFrame = null; if (smap != null) { int[] inputLineInfo = smap.reverseLineMapping.get(elements[i].getLineNumber()); if (inputLineInfo != null && elements[i].getFileName().equals(smap.generatedFileName)) { FileInfo inputFileInfo = smap.fileinfo.get(inputLineInfo[0]); if (inputFileInfo != null) { newFrame = new StackTraceElement("[" + smap.firstStratum + "]", inputFileInfo.path, inputFileInfo.name, inputLineInfo[1]); } } } if (newFrame != null) { if (newElements == null) { newElements = new ArrayList<StackTraceElement>(Arrays.asList(elements).subList(0, i)); } if (keepOriginalFrames) newElements.add(elements[i]); newElements.add(newFrame); } else if (newElements != null) { newElements.add(elements[i]); } } if (newElements != null) { t.setStackTrace(newElements.toArray(new StackTraceElement[newElements.size()])); } if (t.getCause() != null) enhanceStackTrace(t.getCause(), cache, cl, keepOriginalFrames, packageNames); } /** * Extract source debug extension from a class file, provided as an input * stream * * @param in * Input stream to read the class file * @return Source debug extension as a String, or <code>null</code> if none * was found. * @throws IOException * if an I/O error occurs */ // // ASM version of the same method: // private static String extractSourceDebugExtension0(InputStream in) throws IOException { // ClassReader cr = new ClassReader(in); // final String[] result = new String[1]; // cr.accept(new ClassVisitor(Opcodes.ASM4) { // @Override // public void visitSource(String source, String debug) { // result[0] = debug; // } // }, 0); // return result[0]; // } private static String extractSourceDebugExtension(InputStream in) throws IOException { DataInputStream dis = new DataInputStream(in); boolean[] isSourceDebugExtension; dis.skipBytes(8); // read constant pool isSourceDebugExtension = new boolean[dis.readUnsignedShort()]; int[] skipSizes = new int[] { 0, 0, 2, 4, 4, 0, 0, 2, 2, 4, 4, 4, 4, 2, 2, 3, 2, 2, 4 }; for (int i = 1; i < isSourceDebugExtension.length; i++) { byte type = dis.readByte(); int skipSize; if (type == 1) { String value = dis.readUTF(); isSourceDebugExtension[i] = value.equals("SourceDebugExtension"); skipSize = 0; } else if (type == 5 || type == 6) { skipSize = 8; i++; } else if (type > 1 && type < 19) { skipSize = skipSizes[type]; } else { skipSize = 2; } dis.skipBytes(skipSize); } dis.skipBytes(6); int ifaces = dis.readUnsignedShort(); dis.skipBytes(2 * ifaces); // skip fields and methods for (int k = 0; k < 2; k++) { int count = dis.readUnsignedShort(); for (int i = 0; i < count; i++) { dis.skipBytes(6); int attrCount = dis.readUnsignedShort(); for (int j = 0; j < attrCount; j++) { dis.skipBytes(2); int skip = dis.readInt(); dis.skipBytes(skip); } } } // read attributes and find SourceDebugExtension int attrCount = dis.readUnsignedShort(); for (int i = 0; i < attrCount; i++) { int idx = dis.readUnsignedShort(); int len = dis.readInt(); if (isSourceDebugExtension[idx]) { byte[] buf = new byte[len]; dis.readFully(buf); return new String(buf, "UTF-8"); } else { dis.skipBytes(len); } } return null; } private final String generatedFileName, firstStratum; private final Map<Integer, FileInfo> fileinfo = new HashMap<Integer, FileInfo>(); private final Map<Integer, int[]> reverseLineMapping = new HashMap<Integer, int[]>(); private static final Pattern LINE_INFO_PATTERN = Pattern.compile("([0-9]+)(?:#([0-9]+))?(?:,([0-9]+))?:([0-9]+)(?:,([0-9]+))?"); private SMAPSourceDebugExtension(String value) { String[] lines = value.split("\n"); if (!lines[0].equals("SMAP") || !lines[3].startsWith("*S ") || !lines[4].equals("*F")) throw new IllegalArgumentException(value); generatedFileName = lines[1]; firstStratum = lines[3].substring(3); int idx = 5; while (!lines[idx].startsWith("*")) { String infoline = lines[idx++], path = null; if (infoline.startsWith("+ ")) { path = lines[idx++]; infoline = infoline.substring(2); } int pos = infoline.indexOf(" "); int filenum = Integer.parseInt(infoline.substring(0, pos)); String name = infoline.substring(pos + 1); fileinfo.put(filenum, new FileInfo(name, path == null ? name : path)); } if (lines[idx].equals("*L")) { idx++; int lastLFI = 0; while (!lines[idx].startsWith("*")) { Matcher m = LINE_INFO_PATTERN.matcher(lines[idx++]); if (!m.matches()) throw new IllegalArgumentException(lines[idx - 1]); int inputStartLine = Integer.parseInt(m.group(1)); int lineFileID = m.group(2) == null ? lastLFI : Integer.parseInt(m.group(2)); int repeatCount = m.group(3) == null ? 1 : Integer.parseInt(m.group(3)); int outputStartLine = Integer.parseInt(m.group(4)); int outputLineIncrement = m.group(5) == null ? 1 : Integer.parseInt(m.group(5)); for (int i = 0; i < repeatCount; i++) { int[] inputMapping = new int[] { lineFileID, inputStartLine + i }; int baseOL = outputStartLine + i * outputLineIncrement; for (int ol = baseOL; ol < baseOL + outputLineIncrement; ol++) { if (!reverseLineMapping.containsKey(ol)) reverseLineMapping.put(ol, inputMapping); } } lastLFI = lineFileID; } } } private static class FileInfo { public final String name, path; public FileInfo(String name, String path) { this.name = name; this.path = path; } } }
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Not sure what you are trying to achieve here. If you just need to show the jsp and line number in the stack trace during registration, then the simplest would be to replace the logger and show the jsp line number from smap in the print stack trace. Here is the patch for log4j , which is somewhat reminiscent of changes in the stack trace.

Although you will not get automatic navigation from class name to jsp in current IDEs ...

PS: BTW, if you are implementing an SAP parser, it would be nice to contribute to the ASM project ...

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Source: https://habr.com/ru/post/919274/

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