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investigate XML.toString() behavior with null JSONObject values

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stleary 2015-07-17 21:55:50 -05:00
parent ab143af146
commit 6cca292020
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JSONObjectTest.java
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@ -1469,6 +1469,89 @@ public class JSONObjectTest {
assertTrue("Same JSONObject should be equal to itself",
aJsonObject.equals(aJsonObject));
}
@Test
public void jsonObjectNullOperations() {
/**
* The Javadoc for JSONObject.NULL states:
* "JSONObject.NULL is equivalent to the value that JavaScript calls null,
* whilst Java's null is equivalent to the value that JavaScript calls
* undefined."
*
* Standard ECMA-262 6th Edition / June 2015 (included to help explain the javadoc):
* undefined value: primitive value used when a variable has not been assigned a value
* Undefined type: type whose sole value is the undefined value
* null value: primitive value that represents the intentional absence of any object value
* Null type: type whose sole value is the null value
* Java SE8 language spec (included to help explain the javadoc):
* The Kinds of Types and Values ...
* There is also a special null type, the type of the expression null, which has no name.
* Because the null type has no name, it is impossible to declare a variable of the null
* type or to cast to the null type. The null reference is the only possible value of an
* expression of null type. The null reference can always be assigned or cast to any reference type.
* In practice, the programmer can ignore the null type and just pretend that null is merely
* a special literal that can be of any reference type.
* Extensible Markup Language (XML) 1.0 Fifth Edition / 26 November 2008
* No mention of null
* ECMA-404 1st Edition / October 2013:
* JSON Text ...
* These are three literal name tokens: ...
* null
*
* There seems to be no best practice, it's all about what we want the code to do.
* In the code we see that JSONObject.NULL is tranformed into null
*/
// add JSONObject.NULL then convert to string in the manner of XML.toString()
JSONObject jsonObjectJONull = new JSONObject();
Object obj = JSONObject.NULL;
jsonObjectJONull.put("key", obj);
Object value = jsonObjectJONull.opt("key");
assertTrue("opt() JSONObject.NULL should find JSONObject.NULL", obj.equals(value));
value = jsonObjectJONull.get("key");
assertTrue("get() JSONObject.NULL should find JSONObject.NULL", obj.equals(value));
if (value == null) {
value = "";
}
String string = value instanceof String ? (String)value : null;
assertTrue("XML toString() should convert JSONObject.NULL to null", string == null);
// now try it with null
JSONObject jsonObjectNull = new JSONObject();
obj = null;
jsonObjectNull.put("key", obj);
value = jsonObjectNull.opt("key");
assertTrue("opt() null should find null", value == null);;
if (value == null) {
value = "";
}
string = value instanceof String ? (String)value : null;
assertTrue("should convert null to empty string", "".equals(string));
try {
value = jsonObjectNull.get("key");
assertTrue("get() null should throw exception", false);
} catch (Exception ignored) {}
/**
* XML.toString() then goes on to do something with the value
* if the key val is "content", then value.toString() will be
* called. This will evaluate to "null" for JSONObject.NULL,
* and the empty string for null.
* But if the key is anything else, then JSONObject.NULL will be emitted as <key>null</key>
* and null will be emitted as ""
*/
String sJONull = XML.toString(jsonObjectJONull);
assertTrue("JSONObject.NULL should emit a null value", "<key>null</key>".equals(sJONull));
String sNull = XML.toString(jsonObjectNull);
assertTrue("null should emit an empty string", "".equals(sNull));
}
/**
*
*/
private void nullOperations(Object value) {
}
}