Fail on duplicate tags in object

src/main/java/com/ibm/json/java/JSONObject.java

@@ -113,6 +113,19 @@ static public JSONObject parse(InputStream is) throws IOException {
         return parse(isr);
     }
 
+    /**
+     * Convert a String of JSON text into object form. 
+     * @param str The JSON string to parse into a Java Object.
+     * @param duplicateProtection Whether having duplicate keys in an object will throw an error
+     * @return The contructed JSON Object.
+     *
+     * @throws IOEXception Thrown if malformed JSON is read,
+     */
+    static public JSONObject parse(String str, boolean duplicateProtection) throws IOException {
+        StringReader strReader = new StringReader(str);
+        return new Parser(strReader, duplicateProtection).parse();
+    }
+
 
     /**
      * Create a new instance of this class. 

src/main/java/com/ibm/json/java/OrderedJSONObject.java

@@ -99,6 +99,19 @@ static public JSONObject parse(InputStream is) throws IOException {
         return parse(isr);
     }
 
+    /**
+     * Convert a String of JSON text into object form. 
+     * @param str The JSON string to parse into a Java Object.
+     * @param duplicateProtection Whether having duplicate keys in an object will throw an error
+     * @return The contructed JSON Object.  Note that the JSONObject will be an instance of OrderedJSONObject and as such, attribute order is maintained.
+     *
+     * @throws IOEXception Thrown if malformed JSON is read,
+     */
+    static public JSONObject parse(String str, boolean duplicateProtection) throws IOException {
+        StringReader strReader = new StringReader(str);
+        return new Parser(strReader, duplicateProtection).parse(true);
+    }
+
     /**
      * Method to put a JSON'able object into the instance.  Note that the order of initial puts controls the order of serialization.  
      * Meaning that the first time an item is put into the object determines is position of serialization.  Subsequent puts with the same

src/main/java/com/ibm/json/java/internal/Parser.java

@@ -26,6 +26,7 @@ public class Parser
 
     private Tokenizer tokenizer;
     private Token     lastToken;
+    private boolean   duplicateProtection;
 
     /**
      * Contructor
@@ -39,6 +40,11 @@ public Parser(Reader reader) throws IOException {
         this.tokenizer = new Tokenizer(reader);
     }
 
+    public Parser(Reader reader, boolean duplicateProtection) throws IOException {
+        this.tokenizer = new Tokenizer(reader);
+        this.duplicateProtection = duplicateProtection;
+    }
+
     /**
      * Method to initiate the parse of the toplevel JSON object, which will in turn parse all child JSON objects contained within.
      * Same as calling parse(false);
@@ -111,6 +117,11 @@ public JSONObject parseObject(boolean ordered) throws IOException {
             lastToken = tokenizer.next();
             Object val = parseValue(ordered);
 
+            if (duplicateProtection) {
+                if (result.get(key) != null) {
+                    throw new IOException("Duplicate Key \'" + key + "\'");
+                }
+            }
             result.put(key, val);
 
             if (lastToken == Token.TokenComma)

src/test/java/com/ibm/json4j/DuplicateTagTest.java

@@ -0,0 +1,26 @@
+package com.ibm.json4j;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
+
+import java.io.IOException;
+
+import org.junit.Test;
+
+import com.ibm.json.java.JSONObject;
+
+public class DuplicateTagTest {
+
+    @Test
+    public void testDuplicateId() throws IOException {
+        String inputJson = "{\"duplicate\": 123, \"duplicate\": 456}";
+
+        try {
+            JSONObject obj = JSONObject.parse(inputJson, true);
+            fail("Exception should have been thrown");
+        } catch (IOException e) {
+            assertEquals("Duplicate Key \'duplicate\'", e.getMessage());
+        }
+    }
+
+}