Query: add describe and describeParams, test.

Author: greenrobot-team

objectbox-java/src/main/java/io/objectbox/query/Query.java

@@ -62,6 +62,10 @@ public class Query<T> implements Closeable {
 
     native long nativeRemove(long handle, long cursorHandle);
 
+    native String nativeToString(long handle);
+
+    native String nativeDescribeParameters(long handle);
+
     native void nativeSetParameter(long handle, int entityId, int propertyId, @Nullable String parameterAlias,
                                    String value);
 
@@ -654,4 +658,24 @@ public void publish() {
         publisher.publish();
     }
 
+    /**
+     * For logging and testing, returns a string describing this query
+     * like "Query for entity Example with 4 conditions with properties prop1, prop2".
+     * <p>
+     * Note: the format of the returned string may change without notice.
+     */
+    public String describe() {
+        return nativeToString(handle);
+    }
+
+    /**
+     * For logging and testing, returns a string describing the conditions of this query
+     * like "(prop1 == A AND prop2 is null)".
+     * <p>
+     * Note: the format of the returned string may change without notice.
+     */
+    public String describeParameters() {
+        return nativeDescribeParameters(handle);
+    }
+
 }

tests/objectbox-java-test/src/test/java/io/objectbox/query/QueryTest.java

@@ -699,4 +699,25 @@ public void onDbException(Exception e) {
         }
     }
 
+    @Test
+    public void testDescribe() {
+        // Note: description string correctness is fully asserted in core library.
+
+        // No conditions.
+        Query<TestEntity> queryNoConditions = box.query().build();
+        assertEquals("Query for entity TestEntity with 1 conditions",queryNoConditions.describe());
+        assertEquals("TRUE", queryNoConditions.describeParameters());
+
+        // Some conditions.
+        Query<TestEntity> query = box.query()
+                .equal(TestEntity_.simpleString, "Hello")
+                .or().greater(TestEntity_.simpleInt, 42)
+                .build();
+        String describeActual = query.describe();
+        assertTrue(describeActual.startsWith("Query for entity TestEntity with 3 conditions with properties "));
+        // Note: the order properties are listed in is not fixed.
+        assertTrue(describeActual.contains(TestEntity_.simpleString.name));
+        assertTrue(describeActual.contains(TestEntity_.simpleInt.name));
+        assertEquals("(simpleString ==(i) \"Hello\"\n OR simpleInt > 42)", query.describeParameters());
+    }
 }