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https://issues.apache.org/jira/browse/JEXL-250?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16353749#comment-16353749
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Dmitri Blinov edited comment on JEXL-250 at 2/6/18 2:29 PM:
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The following test does not pass for me
{code:java}
@Test
public void test250() throws Exception {
MapContext ctx = new MapContext();
HashMap<Oject,Object> x = new HashMap<Object, Object> ();
x.put(2, "123456789");
ctx.set("x", x);
JexlEngine engine = new
JexlBuilder().strict(true).silent(false).create();
String stmt = "x.2.class.name";
JexlScript script = engine.createScript(stmt);
Object result = script.execute(ctx);
Assert.assertEquals("java.lang.String", result);
try {
stmt = "x.3?.class.name";
script = engine.createScript(stmt);
result = script.execute(ctx);
Assert.assertNull(result);
} catch(JexlException xany) {
Assert.fail("Should have evaluated to null");
}
}
{code}
The test breaks with {{Should have evaluated to null}}
was (Author: dmitri_blinov):
The following test does not pass for me
{code}
@Test
public void test250() throws Exception {
MapContext ctx = new MapContext();
HashMap<Object,Object> x = new HashMap<Object, Object> ();
x.put(2, "123456789");
ctx.set("x", x);
JexlEngine engine = new
JexlBuilder().strict(true).silent(false).create();
String stmt = "x.2.class.name";
JexlScript script = engine.createScript(stmt);
Object result = script.execute(ctx);
Assert.assertEquals("java.lang.String", result);
try {
stmt = "x?.3.class.name";
script = engine.createScript(stmt);
result = script.execute(ctx);
Assert.assertNull(result);
} catch(JexlException xany) {
Assert.fail("Should have evaluated to null");
}
}
{code}
The test breaks with {{Should have evaluated to null}}
> Safe navigation operator
> ------------------------
>
> Key: JEXL-250
> URL: https://issues.apache.org/jira/browse/JEXL-250
> Project: Commons JEXL
> Issue Type: New Feature
> Affects Versions: 3.1
> Reporter: Dmitri Blinov
> Assignee: Henri Biestro
> Priority: Minor
> Fix For: 3.2
>
>
> It would be more convenient for a script writer to have a kind of safe
> navigation operator, in the form of, for example, ({{object?.property),}} for
> null pointer dereferences. I think its quite a common feature of many
> scripting (and compiled languages) now. The safe operator should work like
> basic navigation operator for non null values and should short-circuit the
> entire expression evaluation after encountering null value.
> I see the difference of new operator from the existing lenient mode
> evaluation in ability to explicitly define places in an expression where
> {{null}} deference is allowed, for example the expression
> {code}Order.Customer?.Name{code} defines that each {{Order}} should have a
> {{Customer}} and only the {{Name}} of the {{Customer}} is optional.
> The difference of new operator from the existing null coalescing {{??}}
> operator is in its ability to short-circuit evaluation.
> So, safe navigation operator would be a helpful syntaxic sugar which in my
> opinion does not overlap with an existing functionality.
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