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authorReinier Zwitserloot <reinier@tipit.to>2009-11-25 07:32:49 +0100
committerReinier Zwitserloot <reinier@tipit.to>2009-11-25 07:32:49 +0100
commit1a0e611a9c5e1ee518670647ce1a44beae559b44 (patch)
treee5ef8f671bc6688f486e874d4e2e1a7813e4f0b2 /src/core/lombok/EqualsAndHashCode.java
parent7fd947ea40c25dad9ee543ebc4b92de9a2e05efc (diff)
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+/*
+ * Copyright © 2009 Reinier Zwitserloot and Roel Spilker.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package lombok;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Generates implementations for the {@code equals} and {@code hashCode} methods inherited by all objects.
+ * <p>
+ * If either method already exists, then {@code @EqualsAndHashCode} will not generate that particular method.
+ * If they all exist, {@code @EqualsAndHashCode} generates no methods, and emits a warning instead to highlight
+ * that its doing nothing at all. The parameter list and return type are not relevant when deciding to skip generation of
+ * a method; any method named {@code hashCode} will make {@code @EqualsAndHashCode} not generate that method,
+ * for example.
+ * <p>
+ * By default, all fields that are non-static and non-transient are used in the equality check and hashCode generation.
+ * You can exclude more fields by specifying them in the {@code exclude} parameter. You can also explicitly specify
+ * the fields that are to be used by specifying them in the {@code of} parameter.
+ * <p>
+ * Normally, auto-generating {@code hashCode} and {@code equals} implementations in a subclass is a bad idea, as
+ * the superclass also defines fields, for which equality checks/hashcodes won't be auto-generated. Therefore, a warning
+ * is emitted when you try. Instead, you can set the {@code callSuper} parameter to <em>true</em> which will call
+ * {@code super.equals} and {@code super.hashCode}. Doing this with {@code java.lang.Object} as superclass is
+ * pointless, so, conversely, setting this flag when <em>NOT</em> extending something (other than Object) will also generate
+ * a warning. Be aware that not all implementations of {@code equals} correctly handle being called from a subclass!
+ * Fortunately, lombok-generated {@code equals} implementations do correctly handle it.
+ * <p>
+ * Array fields are handled by way of {@link java.util.Arrays#deepEquals(Object[], Object[])} where necessary, as well
+ * as {@code deepHashCode}. The downside is that arrays with circular references (arrays that contain themselves,
+ * possibly indirectly) results in calls to {@code hashCode} and {@code equals} throwing a
+ * {@link java.lang.StackOverflowError}. However, the implementations for java's own {@link java.util.ArrayList} suffer
+ * from the same flaw.
+ */
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.SOURCE)
+public @interface EqualsAndHashCode {
+ /**
+ * Any fields listed here will not be taken into account in the generated
+ * {@code equals} and {@code hashCode} implementations.
+ * Mutually exclusive with {@link #of()}.
+ */
+ String[] exclude() default {};
+
+ /**
+ * If present, explicitly lists the fields that are to be used for identity.
+ * Normally, all non-static, non-transient fields are used for identity.
+ * <p>
+ * Mutually exclusive with {@link #exclude()}.
+ */
+ String[] of() default {};
+
+ /**
+ * Call on the superclass's implementations of {@code equals} and {@code hashCode} before calculating
+ * for the fields in this class.
+ * <strong>default: false</strong>
+ */
+ boolean callSuper() default false;
+}