Define gerrit-extension-api module

This module will hold a set of thin interfaces that extensions can
build against. Extensions are more lightweight than plugins and have
a smaller surface of the Gerrit server available to them.

Change-Id: I4213004f1ba5c034cf8fc7fbb9f6dd53f3ec8a96

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/annotations/Export.java

@@ -0,0 +1,52 @@
+// Copyright (C) 2012 The Android Open Source Project
+//
+// 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.google.gerrit.extensions.annotations;
+
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import com.google.inject.BindingAnnotation;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+/**
+ * Annotation applied to auto-registered, exported types.
+ * <p>
+ * Plugins or extensions using auto-registration should apply this annotation to
+ * any non-abstract class they want exported for access.
+ * <p>
+ * For SSH commands the @Export annotation names the subcommand:
+ *
+ * <pre>
+ *   @Export("print")
+ *   class MyCommand extends SshCommand {
+ * </pre>
+ *
+ * For HTTP servlets, the @Export annotation names the URL the servlet is bound
+ * to, relative to the plugin or extension's namespace within the Gerrit
+ * container.
+ *
+ * <pre>
+ *  @Export("/index.html")
+ *  class ShowIndexHtml extends HttpServlet {
+ * </pre>
+ */
+@Target({ElementType.TYPE})
+@Retention(RUNTIME)
+@BindingAnnotation
+public @interface Export {
+  String value();
+}

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/annotations/ExportImpl.java

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+// Copyright (C) 2012 The Android Open Source Project
+//
+// 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.google.gerrit.extensions.annotations;
+
+import java.io.Serializable;
+import java.lang.annotation.Annotation;
+
+final class ExportImpl implements Export, Serializable {
+  private static final long serialVersionUID = 0;
+  private final String value;
+
+  ExportImpl(String value) {
+    this.value = value;
+  }
+
+  @Override
+  public Class<? extends Annotation> annotationType() {
+    return Export.class;
+  }
+
+  @Override
+  public String value() {
+    return value;
+  }
+
+  @Override
+  public int hashCode() {
+    return (127 * "value".hashCode()) ^ value.hashCode();
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    return o instanceof Export && value.equals(((Export) o).value());
+  }
+
+  @Override
+  public String toString() {
+    return "@" + Export.class.getName() + "(value=" + value + ")";
+  }
+}

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/annotations/Exports.java

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+// Copyright (C) 2012 The Android Open Source Project
+//
+// 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.google.gerrit.extensions.annotations;
+
+/** Static constructors for {@link Export} annotations. */
+public final class Exports {
+  /** Create an annotation to export under a specific name. */
+  public static Export named(String name) {
+    return new ExportImpl(name);
+  }
+
+  private Exports() {
+  }
+}

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/annotations/PluginName.java

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+// Copyright (C) 2012 The Android Open Source Project
+//
+// 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.google.gerrit.extensions.annotations;
+
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import com.google.inject.BindingAnnotation;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+/**
+ * Annotation applied to a String containing the plugin or extension name.
+ * <p>
+ * A plugin or extension may receive this string by Guice injection to discover
+ * the name that an administrator has installed the plugin or extension under:
+ *
+ * <pre>
+ *  @Inject
+ *  MyType(@PluginName String myName) {
+ *  ...
+ *  }
+ * </pre>
+ */
+@Target({ElementType.PARAMETER, ElementType.FIELD})
+@Retention(RUNTIME)
+@BindingAnnotation
+public @interface PluginName {
+}