Merge pull request #221 from ascrutae/zhangxin/fix/219

Fix OutofMemory of Span.ThrowableTransformer.convert2String

apm-commons/apm-trace/src/main/java/org/skywalking/apm/trace/Span.java

@@ -3,9 +3,8 @@ package org.skywalking.apm.trace;
 import com.google.gson.annotations.Expose;
 import com.google.gson.annotations.SerializedName;
 
-import java.io.ByteArrayOutputStream;
-import java.io.IOException;
 import java.util.*;
+import org.skywalking.apm.trace.util.ThrowableTransformer;
 
 /**
  * Span is a concept from OpenTracing Spec, also from Google Dapper Paper.
@@ -290,32 +289,6 @@ public class Span {
         return log(exceptionFields);
     }
 
-    private enum ThrowableTransformer {
-        INSTANCE;
-
-        private String convert2String(Throwable e, int maxLength) {
-            ByteArrayOutputStream buf = null;
-            StringBuilder expMessage = new StringBuilder();
-            try {
-                buf = new ByteArrayOutputStream();
-                Throwable causeException = e;
-                while (expMessage.length() < maxLength && causeException != null) {
-                    causeException.printStackTrace(new java.io.PrintWriter(buf, true));
-                    expMessage.append(buf.toString());
-                    causeException = causeException.getCause();
-                }
-
-            } finally {
-                try {
-                    buf.close();
-                } catch (IOException ioe) {
-                }
-            }
-
-            return (maxLength > expMessage.length() ? expMessage : expMessage.substring(0, maxLength)).toString();
-        }
-    }
-
     /**
      * This method is from opentracing-java. {@see https://github.com/opentracing/opentracing-java/blob/release-0.20.9/opentracing-api/src/main/java/io/opentracing/Span.java#L120}
      * <p>

apm-commons/apm-trace/src/main/java/org/skywalking/apm/trace/util/ThrowableTransformer.java

+package org.skywalking.apm.trace.util;
+
+/**
+ * {@link ThrowableTransformer} is responsible for transferring stack trace of throwable.
+ */
+public enum ThrowableTransformer {
+    INSTANCE;
+
+    private static final String LINE_SEPARATOR = System.getProperty("line.separator");
+
+    public String convert2String(Throwable throwable, final int maxLength) {
+        final StringBuilder stackMessage = new StringBuilder();
+        Throwable causeException = throwable;
+        while (causeException != null) {
+            stackMessage.append(printExceptionInfo(causeException));
+
+            boolean overMaxLength = printStackElement(throwable.getStackTrace(), new AppendListener() {
+                public void append(String value) {
+                    stackMessage.append(value);
+                }
+
+                public boolean overMaxLength() {
+                    return stackMessage.length() > maxLength;
+                }
+            });
+
+            if (overMaxLength) {
+                break;
+            }
+
+            causeException = throwable.getCause();
+        }
+
+        return stackMessage.toString();
+    }
+
+    private String printExceptionInfo(Throwable causeException) {
+        return causeException.toString() + LINE_SEPARATOR;
+    }
+
+    private boolean printStackElement(StackTraceElement[] stackTrace, AppendListener printListener) {
+        for (StackTraceElement traceElement : stackTrace) {
+            printListener.append("at " + traceElement + LINE_SEPARATOR);
+            if (printListener.overMaxLength()) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private interface AppendListener {
+        void append(String value);
+
+        boolean overMaxLength();
+    }
+}