Support suppressed exceptions in throwable converter

logback-classic/src/main/java/ch/qos/logback/classic/pattern/ThrowableProxyConverter.java

@@ -34,6 +34,8 @@
  */
 public class ThrowableProxyConverter extends ThrowableHandlingConverter {
 
+  protected static final int BUILDER_CAPACITY = 2048;
+
   int lengthOption;
   List<EventEvaluator<ILoggingEvent>> evaluatorList = null;
 
@@ -137,18 +139,41 @@ public String convert(ILoggingEvent event) {
   }
 
   protected String throwableProxyToString(IThrowableProxy tp) {
-    StringBuilder buf = new StringBuilder(32);
-    IThrowableProxy currentThrowable = tp;
-    while (currentThrowable != null) {
-      subjoinThrowableProxy(buf, currentThrowable);
-      currentThrowable = currentThrowable.getCause();
+    StringBuilder sb = new StringBuilder(BUILDER_CAPACITY);
+
+    recursiveAppend(sb, null, ThrowableProxyUtil.REGULAR_EXCEPTION_INDENT, tp);
+
+    return sb.toString();
+  }
+
+  private void recursiveAppend(StringBuilder sb, String prefix, int indent, IThrowableProxy tp) {
+    if(tp == null)
+      return;
+    subjoinFirstLine(sb, prefix, indent, tp);
+    sb.append(CoreConstants.LINE_SEPARATOR);
+    subjoinSTEPArray(sb, indent, tp);
+    IThrowableProxy[] suppressed = tp.getSuppressed();
+    if(suppressed != null) {
+      for(IThrowableProxy current : suppressed) {
+        recursiveAppend(sb, CoreConstants.SUPPRESSED, indent + ThrowableProxyUtil.SUPPRESSED_EXCEPTION_INDENT, current);
+      }
     }
-    return buf.toString();
+    recursiveAppend(sb, CoreConstants.CAUSED_BY, indent, tp.getCause());
+  }
+
+  private void subjoinFirstLine(StringBuilder buf, String prefix, int indent, IThrowableProxy tp) {
+    ThrowableProxyUtil.indent(buf, indent - 1);
+    if (prefix != null) {
+      buf.append(prefix);
+    }
+    subjoinExceptionMessage(buf, tp);
+  }
+
+  private void subjoinExceptionMessage(StringBuilder buf, IThrowableProxy tp) {
+    buf.append(tp.getClassName()).append(": ").append(tp.getMessage());
   }
 
-  void subjoinThrowableProxy(StringBuilder buf, IThrowableProxy tp) {
-    ThrowableProxyUtil.subjoinFirstLine(buf, tp);
-    buf.append(CoreConstants.LINE_SEPARATOR);
+  private void subjoinSTEPArray(StringBuilder buf, int indent, IThrowableProxy tp) {
     StackTraceElementProxy[] stepArray = tp.getStackTraceElementProxyArray();
     int commonFrames = tp.getCommonFrames();
 
@@ -161,15 +186,15 @@ void subjoinThrowableProxy(StringBuilder buf, IThrowableProxy tp) {
     }
 
     for (int i = 0; i < maxIndex; i++) {
-      String string = stepArray[i].toString();
-      buf.append(CoreConstants.TAB);
-      buf.append(string);
+      ThrowableProxyUtil.indent(buf, indent);
+      buf.append(stepArray[i]);
       extraData(buf, stepArray[i]); // allow other data to be added
       buf.append(CoreConstants.LINE_SEPARATOR);
     }
 
     if (commonFrames > 0 && unrestrictedPrinting) {
-      buf.append("\t... ").append(tp.getCommonFrames()).append(
+      ThrowableProxyUtil.indent(buf, indent);
+      buf.append("... ").append(tp.getCommonFrames()).append(
               " common frames omitted").append(CoreConstants.LINE_SEPARATOR);
     }
   }

logback-classic/src/main/java/ch/qos/logback/classic/spi/ThrowableProxyUtil.java

@@ -17,14 +17,15 @@
 
 /**
  * Convert a throwable into an array of ThrowableDataPoint objects.
- * 
- * 
+ *
+ *
  * @author Ceki Gülcü
  */
 public class ThrowableProxyUtil {
 
   public static final int REGULAR_EXCEPTION_INDENT = 1;
-  public static final int SUPPRESSED_EXCEPTION_INDENT = 2;
+  public static final int SUPPRESSED_EXCEPTION_INDENT = 1;
+  private static final int BUILDER_CAPACITY = 2048;
 
   public static void build(ThrowableProxy nestedTP, Throwable nestedThrowable,
       ThrowableProxy parentTP) {
@@ -76,7 +77,7 @@ static int findNumberOfCommonFrames(StackTraceElement[] steArray,
   }
 
   public static String asString(IThrowableProxy tp) {
-    StringBuilder sb = new StringBuilder();
+    StringBuilder sb = new StringBuilder(BUILDER_CAPACITY);
 
     recursiveAppend(sb, null, REGULAR_EXCEPTION_INDENT, tp);
 
@@ -86,19 +87,26 @@ public static String asString(IThrowableProxy tp) {
   private static void recursiveAppend(StringBuilder sb, String prefix, int indent, IThrowableProxy tp) {
     if(tp == null)
       return;
-    subjoinFirstLine(sb, prefix, tp);
+    subjoinFirstLine(sb, prefix, indent, tp);
     sb.append(CoreConstants.LINE_SEPARATOR);
     subjoinSTEPArray(sb, indent, tp);
     IThrowableProxy[] suppressed = tp.getSuppressed();
     if(suppressed != null) {
       for(IThrowableProxy current : suppressed) {
-        recursiveAppend(sb, CoreConstants.SUPPRESSED, SUPPRESSED_EXCEPTION_INDENT, current);
+        recursiveAppend(sb, CoreConstants.SUPPRESSED, indent + SUPPRESSED_EXCEPTION_INDENT, current);
       }
     }
-    recursiveAppend(sb, CoreConstants.CAUSED_BY, REGULAR_EXCEPTION_INDENT, tp.getCause());
+    recursiveAppend(sb, CoreConstants.CAUSED_BY, indent, tp.getCause());
+  }
+
+  public static void indent(StringBuilder buf, int indent) {
+    for(int j = 0; j < indent; j++) {
+      buf.append(CoreConstants.TAB);
+    }
   }
 
-  private static void subjoinFirstLine(StringBuilder buf, String prefix, IThrowableProxy tp) {
+  private static void subjoinFirstLine(StringBuilder buf, String prefix, int indent, IThrowableProxy tp) {
+    indent(buf, indent - 1);
     if (prefix != null) {
       buf.append(prefix);
     }
@@ -114,13 +122,13 @@ public static void subjoinPackagingData(StringBuilder builder, StackTraceElement
         } else {
           builder.append(" [");
         }
-   
+
         builder.append(cpd.getCodeLocation()).append(':').append(
             cpd.getVersion()).append(']');
       }
     }
   }
-  
+
   public static void subjoinSTEP(StringBuilder sb, StackTraceElementProxy step) {
     sb.append(step.toString());
     subjoinPackagingData(sb, step);
@@ -138,7 +146,7 @@ public static void subjoinSTEPArray(StringBuilder sb, IThrowableProxy tp) {
 
   /**
    * @param sb The StringBuilder the STEPs are appended to.
-   * @param indentLevel indentation level used for the STEPs, usually either REGULAR_EXCEPTION_INDENT or SUPPRESSED_EXCEPTION_INDENT.
+   * @param indentLevel indentation level used for the STEPs, usually REGULAR_EXCEPTION_INDENT.
    * @param tp the IThrowableProxy containing the STEPs.
    */
   public static void subjoinSTEPArray(StringBuilder sb, int indentLevel, IThrowableProxy tp) {
@@ -147,21 +155,17 @@ public static void subjoinSTEPArray(StringBuilder sb, int indentLevel, IThrowabl
 
     for (int i = 0; i < stepArray.length - commonFrames; i++) {
       StackTraceElementProxy step = stepArray[i];
-      for(int j = 0; j < indentLevel ; j++) {
-        sb.append(CoreConstants.TAB);
-      }
+      indent(sb, indentLevel);
       subjoinSTEP(sb, step);
       sb.append(CoreConstants.LINE_SEPARATOR);
     }
-    
+
     if (commonFrames > 0) {
-      for(int j = 0; j < indentLevel ; j++) {
-        sb.append(CoreConstants.TAB);
-      }
+      indent(sb, indentLevel);
       sb.append("... ").append(commonFrames).append(" common frames omitted")
           .append(CoreConstants.LINE_SEPARATOR);
     }
-    
+
   }
 
   public static void subjoinFirstLine(StringBuilder buf, IThrowableProxy tp) {

logback-classic/src/test/java/ch/qos/logback/classic/spi/ThrowableProxyTest.java

@@ -127,6 +127,23 @@ public void suppressedWithCause() throws InvocationTargetException, IllegalAcces
     verify(ex);
   }
 
+  @Test
+  public void suppressedWithSuppressed() throws Exception
+  {
+    assumeNotNull(ADD_SUPPRESSED_METHOD); // only execute on Java 7, would work anyway but doesn't make sense.
+    Exception ex = null;
+    try {
+      someMethod();
+    } catch (Exception e) {
+      ex=new Exception("Wrapper", e);
+      Exception fooException = new Exception("Foo");
+      Exception barException = new Exception("Bar");
+      addSuppressed(barException, fooException);
+      addSuppressed(e, barException);
+    }
+    verify(ex);
+  }
+
   // see also http://jira.qos.ch/browse/LBCLASSIC-216
   @Test
   public void nullSTE() {

logback-core/src/main/java/ch/qos/logback/core/CoreConstants.java

@@ -85,7 +85,7 @@ public class CoreConstants {
    */
   public static final Class<?>[] EMPTY_CLASS_ARRAY = new Class[]{};
   public static final String CAUSED_BY = "Caused by: ";
-  public static final String SUPPRESSED = "\tSuppressed: ";
+  public static final String SUPPRESSED = "Suppressed: ";
   public static final String WRAPPED_BY = "Wrapped by: ";
 
   public static final char PERCENT_CHAR = '%';