Revised Gson to refuse to deserialize floating point numbers into integer types.

This is probably a break from the past: previous versions of Gson allowed truncating a floating point into a long or int. However, it wasn't consistent in this behavior. It disallowed converting a BigDecimal value into BigInteger, int or long. Refusing to deserialize such values is aligned with fail-fast approach of uncovering bugs.

gson/src/main/java/com/google/gson/JsonPrimitive.java

@@ -213,7 +213,8 @@ public final class JsonPrimitive extends JsonElement {
    */
   @Override
   public BigInteger getAsBigInteger() {
-    return value instanceof BigInteger ? (BigInteger) value : new BigInteger(value.toString());
+    return value instanceof BigInteger ?
+        (BigInteger) value : new BigInteger(value.toString());
   }
 
   /**

gson/src/main/java/com/google/gson/LazilyParsedNumber.java

@@ -15,6 +15,8 @@
  */
 package com.google.gson;
 
+import java.math.BigInteger;
+
 /**
  * This class holds a number value that is lazily converted to a specific number type
  *
@@ -30,12 +32,24 @@ final class LazilyParsedNumber extends Number {
 
   @Override
   public int intValue() {
-    return Integer.parseInt(value);
+    try {
+      return Integer.parseInt(value);
+    } catch (NumberFormatException e) {
+      try {
+        return (int) Long.parseLong(value);
+      } catch (NumberFormatException nfe) {
+        return new BigInteger(value).intValue(); 
+      }
+    }
   }
 
   @Override
   public long longValue() {
-    return Long.parseLong(value);
+    try {
+      return Long.parseLong(value);
+    } catch (NumberFormatException e) {
+      return new BigInteger(value).longValue(); 
+    }
   }
 
   @Override

gson/src/test/java/com/google/gson/functional/PrimitiveTest.java

@@ -38,6 +38,9 @@ import java.math.BigInteger;
  * @author Joel Leitch
  */
 public class PrimitiveTest extends TestCase {
+  private static final BigInteger MAX_INT_VALUE = new BigInteger("2147483647");
+  private static final BigInteger MAX_LONG_VALUE = new BigInteger("9223372036854775807");
+
   private Gson gson;
 
   @Override
@@ -757,4 +760,68 @@ public class PrimitiveTest extends TestCase {
       fail();
     } catch (JsonSyntaxException expected) {}
   }
+
+  public void testDeserializingDecimalPointValuesAsIntegerFails() {
+    try {
+      gson.fromJson("1.0", Integer.class);
+      fail();
+    } catch (JsonParseException expected) {
+    }
+  }
+
+  public void testDeserializingBigDecimalAsIntegerFails() {
+    try {
+      gson.fromJson("-122.08e-213", Integer.class);
+      fail();
+    } catch (JsonParseException expected) {
+    }
+  }
+
+  public void testDeserializingBigIntegerAsInteger() {
+    String bigIntegerValue = "12121211243123245845384534687435634558945453489543985435";
+    int actual = gson.fromJson(bigIntegerValue, Integer.class);
+    int expected = new BigInteger(bigIntegerValue).and(MAX_INT_VALUE).intValue();
+    assertEquals(expected, actual);
+  }
+
+  public void testDeserializingBigIntegerAsLong() {
+    String bigIntegerValue = "12121211243123245845384534687435634558945453489543985435";
+    long actual = gson.fromJson(bigIntegerValue, long.class);
+    long expected = new BigInteger(bigIntegerValue).and(MAX_LONG_VALUE).longValue();
+    assertEquals(expected, actual);
+  }
+
+  public void testDeserializingBigDecimalAsLongFails() {
+    try {
+      gson.fromJson("-122.08e-2132", long.class);
+      fail();
+    } catch (JsonParseException expected) {
+    }
+  }
+
+  public void testDeserializingBigDecimalAsFloat() {
+    String json = "-122.08e-2132332";
+    float actual = gson.fromJson(json, float.class);
+    assertEquals(-0.0f, actual);
+  }
+
+  public void testDeserializingBigDecimalAsDouble() {
+    String json = "-122.08e-2132332";
+    double actual = gson.fromJson(json, double.class);
+    assertEquals(-0.0d, actual);
+  }
+
+  public void testDeserializingBigDecimalAsBigIntegerFails() {
+    try {
+      gson.fromJson("-122.08e-213", BigInteger.class);
+      fail();
+    } catch (JsonParseException expected) {
+    }
+  }
+
+  public void testDeserializingBigIntegerAsBigDecimal() {
+    BigDecimal actual =
+      gson.fromJson("12121211243123245845384534687435634558945453489543985435", BigDecimal.class);
+    assertEquals("12121211243123245845384534687435634558945453489543985435", actual.toPlainString());
+  }
 }