add Expression.equalTo() and Expression.notEqualTo()

see #438.

api/src/main/java/jakarta/persistence/criteria/Expression.java

@@ -11,6 +11,7 @@
  */
 
 // Contributors:
+//     Gavin King      - 3.2
 //     Linda DeMichiel - 2.1
 //     Linda DeMichiel - 2.0
 
@@ -40,6 +41,38 @@ public interface Expression<T> extends Selection<T> {
      */
     Predicate isNotNull();
 
+    /**
+     * Create a predicate to test whether the expression is equal to
+     * the argument.
+     * @param value  expression to be tested against
+     * @return predicate testing for equality
+     */
+    Predicate equalTo(Expression<?> value);
+
+    /**
+     * Create a predicate to test whether the expression is equal to
+     * the argument.
+     * @param value  value to be tested against
+     * @return predicate testing for equality
+     */
+    Predicate equalTo(Object value);
+
+    /**
+     * Create a predicate to test whether the expression is unequal
+     * to the argument.
+     * @param value  expression to be tested against
+     * @return predicate testing for inequality
+     */
+    Predicate notEqualTo(Expression<?> value);
+
+    /**
+     * Create a predicate to test whether the expression is unequal
+     * to the argument.
+     * @param value  value to be tested against
+     * @return predicate testing for inequality
+     */
+    Predicate notEqualTo(Object value);
+
     /**
      * Create a predicate to test whether the expression is a member
      * of the argument list.

spec/src/main/asciidoc/appendixes.adoc

@@ -110,6 +110,8 @@ Added `||` string concatenation operator
 
 Added _getSingleResultOrNull()_ to _Query_, _TypedQuery_, _StoredProcedureQuery_
 
+Added _equalTo()_ and _notEqualTo()_ to _Expression_
+
 Added _concat()_ overload accepting list of expressions to _CriteriaBuilder_
 
 Made the _name_ member of _TableGenerator_ and _SequenceGenerator_ optional

spec/src/main/asciidoc/ch06-criteria-api.adoc

@@ -2767,6 +2767,38 @@ public interface Expression<T> extends Selection<T> {
      */
     Predicate isNotNull();
 
+    /**
+     * Create a predicate to test whether the expression is equal to
+     * the argument.
+     * @param value  expression to be tested against
+     * @return predicate testing for equality
+     */
+    Predicate equalTo(Expression<?> value);
+
+    /**
+     * Create a predicate to test whether the expression is equal to
+     * the argument.
+     * @param value  value to be tested against
+     * @return predicate testing for equality
+     */
+    Predicate equalTo(Object value);
+
+    /**
+     * Create a predicate to test whether the expression is unequal
+     * to the argument.
+     * @param value  expression to be tested against
+     * @return predicate testing for inequality
+     */
+    Predicate notEqualTo(Expression<?> value);
+
+    /**
+     * Create a predicate to test whether the expression is unequal
+     * to the argument.
+     * @param value  value to be tested against
+     * @return predicate testing for inequality
+     */
+    Predicate notEqualTo(Object value);
+
     /**
      * Create a predicate to test whether the expression is a member
      * of the argument list.