Support StreamWriteConstraints (#602)

Author: pjfanning

src/main/java/com/fasterxml/jackson/dataformat/xml/ser/ToXmlGenerator.java

@@ -321,6 +321,11 @@ public JsonGenerator overrideFormatFeatures(int values, int mask)
     /**********************************************************
      */
 
+    @Override
+    public StreamWriteConstraints streamWriteConstraints() {
+        return _ioContext.streamWriteConstraints();
+    }
+
     public ToXmlGenerator enable(Feature f) {
         _formatFeatures |= f.getMask();
         return this;
@@ -536,6 +541,7 @@ public final void writeStartArray() throws IOException
     {
         _verifyValueWrite("start an array");
         _writeContext = _writeContext.createChildArrayContext();
+        streamWriteConstraints().validateNestingDepth(_writeContext.getNestingDepth());
         if (_cfgPrettyPrinter != null) {
             _cfgPrettyPrinter.writeStartArray(this);
         } else {
@@ -562,6 +568,7 @@ public final void writeStartObject() throws IOException
     {
         _verifyValueWrite("start an object");
         _writeContext = _writeContext.createChildObjectContext();
+        streamWriteConstraints().validateNestingDepth(_writeContext.getNestingDepth());
         if (_cfgPrettyPrinter != null) {
             _cfgPrettyPrinter.writeStartObject(this);
         } else {

src/test/java/com/fasterxml/jackson/dataformat/xml/ser/dos/CyclicDataSerTest.java

@@ -0,0 +1,32 @@
+package com.fasterxml.jackson.dataformat.xml.ser.dos;
+
+import com.fasterxml.jackson.core.StreamWriteConstraints;
+import com.fasterxml.jackson.databind.JsonMappingException;
+import com.fasterxml.jackson.dataformat.xml.XmlMapper;
+import com.fasterxml.jackson.dataformat.xml.XmlTestBase;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Simple unit tests to verify that we fail gracefully if you attempt to serialize
+ * data that is cyclic (eg a list that contains itself).
+ */
+public class CyclicDataSerTest extends XmlTestBase
+{
+    private final XmlMapper MAPPER = newMapper();
+
+    public void testListWithSelfReference() throws Exception {
+        List<Object> list = new ArrayList<>();
+        list.add(list);
+        try {
+            MAPPER.writeValueAsString(list);
+            fail("expected JsonMappingException");
+        } catch (JsonMappingException jmex) {
+            String exceptionPrefix = String.format("Document nesting depth (%d) exceeds the maximum allowed",
+                    StreamWriteConstraints.DEFAULT_MAX_DEPTH + 1);
+            assertTrue("JsonMappingException message is as expected?",
+                    jmex.getMessage().startsWith(exceptionPrefix));
+        }
+    }
+}