From 8365fcc3a5b2285fc1fe442d6f2eb8a90cbbab3a Mon Sep 17 00:00:00 2001
From: "Brian S. O'Neill" <bronee@gmail.com>
Date: Wed, 30 Aug 2006 01:50:06 +0000
Subject: Add standard capabilities

---
 .../carbonado/constraint/ConstraintDefinition.java | 111 +++++++++++++++++++++
 1 file changed, 111 insertions(+)
 create mode 100644 src/main/java/com/amazon/carbonado/constraint/ConstraintDefinition.java

(limited to 'src/main/java/com/amazon/carbonado/constraint/ConstraintDefinition.java')

diff --git a/src/main/java/com/amazon/carbonado/constraint/ConstraintDefinition.java b/src/main/java/com/amazon/carbonado/constraint/ConstraintDefinition.java
new file mode 100644
index 0000000..22514fc
--- /dev/null
+++ b/src/main/java/com/amazon/carbonado/constraint/ConstraintDefinition.java
@@ -0,0 +1,111 @@
+/*
+ * Copyright 2006 Amazon Technologies, Inc. or its affiliates.
+ * Amazon, Amazon.com and Carbonado are trademarks or registered trademarks
+ * of Amazon Technologies, Inc. or its affiliates.  All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.amazon.carbonado.constraint;
+
+import java.lang.annotation.*;
+
+/**
+ * Allows annotations to be defined that restrict property values. The
+ * annotation is just a pointer to a constraint checking class. If the
+ * constraint class is not explicitly provided, it defaults to a static inner
+ * class named "Constraint" in the annotation itself.
+ *
+ * <p>The constraint class must have a public constructor that accepts the
+ * annotation that has the ConstraintDefinition annotation. It must also define
+ * several "constrain" methods which perform constraint checks on specific
+ * property types.
+ * <p>
+ * Example integer constraint:
+ * <pre>
+ * &#64;Documented
+ * <b>&#64;Retention(RetentionPolicy.RUNTIME)</b>
+ * <b>&#64;Target(ElementType.METHOD)</b>
+ * <b>&#64;ConstraintDefinition</b>
+ * public &#64;interface IntegerConstraint {
+ *     int min() default Integer.MIN_VALUE;
+ *
+ *     int max() default Integer.MAX_VALUE;
+ *
+ *     public static class Constraint {
+ *         private final String propertyName;
+ *         private final int min;
+ *         private final int max;
+ *
+ *         // Constructor may throw a MalformedTypeException if
+ *         // params supplied by annotation are illegal.
+ *
+ *         /**
+ *          * @param type optional type of object that contains the constrained property
+ *          * @param propertyName name of property with constraint
+ *          * @param annotation specific annotation that binds to this constraint class
+ *          *&#47;
+ *         public Constraint(Class type, String propertyName, IntegerConstraint annotation) {
+ *             this.propertyName = propertyName;
+ *             this.min = annotation.min();
+ *             this.max = annotation.max();
+ *         }
+ *
+ *         // Define a constrain method for each supported property type.
+ *
+ *         /**
+ *          * @param propertyValue specific value to constrain
+ *          *&#47;
+ *         public void constrain(int propertyValue) throws IllegalArgumentException {
+ *             if (propertyValue < min || propertyValue > max) {
+ *                 throw new IllegalArgumentException
+ *                     ("Value for \"" + propertyName + "\" must be in range " +
+ *                      min + ".." + max + ": " + propertyValue);
+ *             }
+ *         }
+ *     }
+ * }
+ * </pre>
+ *
+ * The newly defined integer constraint can be applied to property mutators.
+ *
+ * <pre>
+ * public interface UserInfo extends Storable {
+ *     ...
+ *
+ *     // Constraint is called before setting age.
+ *     <b>&#64;IntegerConstraint(min=0, max=120)</b>
+ *     void setAge(int value);
+ * }
+ * </pre>
+ *
+ * @author Brian S O'Neill
+ */
+@Documented
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.ANNOTATION_TYPE)
+public @interface ConstraintDefinition {
+    /**
+     * Specify class which will perform constraint checking. Must have a public
+     * constructor with the signature
+     * <code>(Class type, String propertyName, <i>Annotation</i>)</code>,
+     * where <code><i>Annotation</i></code> refers to the annotation with the
+     * constraint definition.
+     *
+     * <p>The implementation class need not be explicitly specified. By
+     * default, the constraint class must be a static inner class of the
+     * annotation, named "Constraint".
+     */
+    // Use void.class to mean default.
+    Class implementation() default void.class;
+}
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