#57 Fix out-of-bounds exception thrown while rendering stack traces.

Author: vy

CHANGELOG.md

@@ -1,3 +1,8 @@
+### (2020-??-??) v1.0.2
+
+- Fix `ArrayIndexOutOfBoundsException` thrown when `stackTrace:text` produces
+  an output violating the truncation limit. (#57)
+
 ### (2020-01-21) v1.0.1
 
 - Fix NPE in `StringTruncatingGeneratorDelegate`. (#53)

README.md

@@ -538,6 +538,7 @@ Let us try to answer some common questions:
 
 - [bakomchik](https://github.com/bakomchik)
 - [chrissydee](https://github.com/chrissydee)
+- [Daniel Lundsgaard Skovenborg](https://github.com/waldeinburg)
 - [Eric Schwartz](https://github.com/emschwar)
 - [Felix Barnsteiner](https://github.com/felixbarny)
 - [Johann Schmitz](https://github.com/ercpe)

layout/src/main/java/com/vlkan/log4j2/logstash/layout/util/BufferedPrintWriter.java

@@ -44,6 +44,10 @@ public int getCapacity() {
         return bufferedWriter.getCapacity();
     }
 
+    public boolean isOverflow() {
+        return bufferedWriter.isOverflow();
+    }
+
     @Override
     public void close() {
         bufferedWriter.close();

layout/src/main/java/com/vlkan/log4j2/logstash/layout/util/BufferedWriter.java

@@ -24,9 +24,12 @@ public final class BufferedWriter extends Writer {
 
     private int position;
 
+    private boolean overflow;
+
     BufferedWriter(int capacity) {
         this.buffer = new char[capacity];
         this.position = 0;
+        this.overflow = false;
     }
 
     char[] getBuffer() {
@@ -41,10 +44,23 @@ int getCapacity() {
         return buffer.length;
     }
 
+    boolean isOverflow() {
+        return overflow;
+    }
+
     @Override
     public void write(char[] source, int offset, int length) {
-        System.arraycopy(source, offset, buffer, position, length);
-        position += length;
+        if (!overflow) {
+            int limit = buffer.length - position;
+            if (length > limit) {
+                overflow = true;
+                System.arraycopy(source, offset, buffer, position, limit);
+                position = buffer.length;
+            } else {
+                System.arraycopy(source, offset, buffer, position, length);
+                position += length;
+            }
+        }
     }
 
     @Override
@@ -53,6 +69,7 @@ public void flush() {}
     @Override
     public void close() {
         position = 0;
+        overflow = false;
     }
 
 }

layout/src/test/java/com/vlkan/log4j2/logstash/layout/LogstashLayoutTest.java

@@ -1407,4 +1407,39 @@ private static LogEvent createLogEventAtInstant(String formattedInstant) {
                 .build();
     }
 
+    @Test
+    public void test_StackTraceTextResolver_with_maxStringLength() throws Exception {
+
+        // Create the event template.
+        ObjectNode eventTemplateRootNode = JSON_NODE_FACTORY.objectNode();
+        eventTemplateRootNode.put("stackTrace", "${json:exception:stackTrace:text}");
+        String eventTemplate = eventTemplateRootNode.toString();
+
+        // Create the layout.
+        int maxStringLength = eventTemplate.length();
+        Configuration configuration = ConfigurationBuilderFactory.newConfigurationBuilder().build();
+        LogstashLayout layout = LogstashLayout
+                .newBuilder()
+                .setConfiguration(configuration)
+                .setEventTemplate(eventTemplate)
+                .setMaxStringLength(maxStringLength)
+                .setStackTraceEnabled(true)
+                .build();
+
+        // Create the log event.
+        SimpleMessage message = new SimpleMessage("foo");
+        LogEvent logEvent = Log4jLogEvent
+                .newBuilder()
+                .setLoggerName(LogstashLayoutTest.class.getSimpleName())
+                .setMessage(message)
+                .setThrown(NonAsciiUtf8MethodNameContainingException.INSTANCE)
+                .build();
+
+        // Check the serialized event.
+        String serializedLogEvent = layout.toSerializable(logEvent);
+        JsonNode rootNode = OBJECT_MAPPER.readTree(serializedLogEvent);
+        assertThat(point(rootNode, "stackTrace").asText()).isNotBlank();
+
+    }
+
 }