APT hello world. This generates an empty class for each class annotated @GeneratedTypeAdapter.

gson/gson-codegen/pom.xml

@@ -37,12 +37,6 @@
     <url>http://www.google.com</url>
   </organization>
   <dependencies>
-    <dependency>
-      <groupId>com.google.code.gson</groupId>
-      <artifactId>gson</artifactId>
-      <version>2.2.3-SNAPSHOT</version>
-      <scope>compile</scope>
-    </dependency>
     <dependency>
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>
@@ -90,6 +84,7 @@
         <configuration>
           <source>1.5</source>
           <target>1.5</target>
+          <compilerArgument>-proc:none</compilerArgument>
         </configuration>
       </plugin>
       <plugin>

gson/gson-codegen/src/main/java/com/google/gson/codegen/CodeGen.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2012 Square, Inc.
+ *
+ * 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.gson.codegen;
+
+import javax.lang.model.element.Element;
+import javax.lang.model.element.ElementKind;
+import javax.lang.model.element.PackageElement;
+import javax.lang.model.element.TypeElement;
+
+public class CodeGen {
+  private CodeGen() {
+  }
+
+  public static PackageElement getPackage(Element type) {
+    while (type.getKind() != ElementKind.PACKAGE) {
+      type = type.getEnclosingElement();
+    }
+    return (PackageElement) type;
+  }
+
+  /**
+   * Returns a fully qualified class name to complement {@code type}.
+   */
+  public static String adapterName(TypeElement typeElement, String suffix) {
+    StringBuilder builder = new StringBuilder();
+    rawTypeToString(builder, typeElement, '$');
+    builder.append(suffix);
+    return builder.toString();
+  }
+
+  static void rawTypeToString(StringBuilder result, TypeElement type, char innerClassSeparator) {
+    String packageName = getPackage(type).getQualifiedName().toString();
+    String qualifiedName = type.getQualifiedName().toString();
+    result.append(packageName);
+    result.append('.');
+    result.append(
+        qualifiedName.substring(packageName.length() + 1).replace('.', innerClassSeparator));
+  }
+}

gson/gson-codegen/src/main/java/com/google/gson/codegen/GeneratedTypeAdapter.java

@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) 2012 Google Inc.
+ *
+ * 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.gson.codegen;
+
+public @interface GeneratedTypeAdapter {
+  Class<?>[] value() default {};
+}

gson/gson-codegen/src/main/java/com/google/gson/codegen/GeneratedTypeAdapterProcessor.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2012 Google Inc.
+ *
+ * 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.gson.codegen;
+
+import java.io.IOException;
+import java.util.Set;
+import javax.annotation.processing.AbstractProcessor;
+import javax.annotation.processing.RoundEnvironment;
+import javax.annotation.processing.SupportedAnnotationTypes;
+import javax.annotation.processing.SupportedSourceVersion;
+import javax.lang.model.SourceVersion;
+import javax.lang.model.element.Element;
+import javax.lang.model.element.TypeElement;
+import javax.tools.Diagnostic;
+import javax.tools.JavaFileObject;
+
+import static java.lang.reflect.Modifier.FINAL;
+
+@SupportedAnnotationTypes("com.google.gson.codegen.GeneratedTypeAdapter")
+@SupportedSourceVersion(SourceVersion.RELEASE_6)
+public final class GeneratedTypeAdapterProcessor extends AbstractProcessor {
+  @Override public boolean process(Set<? extends TypeElement> types, RoundEnvironment env) {
+    try {
+      for (Element element : env.getElementsAnnotatedWith(GeneratedTypeAdapter.class)) {
+        writeAdapter((TypeElement) element);
+      }
+    } catch (IOException e) {
+      processingEnv.getMessager().printMessage(Diagnostic.Kind.ERROR, e.getMessage());
+    }
+    return true;
+  }
+
+  private void writeAdapter(TypeElement type) throws IOException {
+    String typeAdapterName = CodeGen.adapterName(type, "$TypeAdapter");
+    JavaFileObject sourceFile = processingEnv.getFiler()
+        .createSourceFile(typeAdapterName, type);
+
+    JavaWriter writer = new JavaWriter(sourceFile.openWriter());
+    writer.addPackage(CodeGen.getPackage(type).getQualifiedName().toString());
+    writer.beginType(typeAdapterName, "class", FINAL, null);
+    writer.endType();
+    writer.close();
+  }
+}

gson/gson-codegen/src/main/java/com/google/gson/codegen/JavaWriter.java

@@ -0,0 +1,443 @@
+/**
+ * Copyright (C) 2012 Square, Inc.
+ *
+ * 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.gson.codegen;
+
+import java.io.IOException;
+import java.io.Writer;
+import java.lang.annotation.Annotation;
+import java.lang.reflect.Modifier;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * Emits Java source files.
+ */
+public final class JavaWriter {
+  private static final Pattern TYPE_PATTERN = Pattern.compile("(?:[\\w$]+\\.)*([\\w$]+)");
+  private static final String INDENT = "  ";
+
+  /** Map fully qualified type names to their short names. */
+  private final Map<String, String> importedTypes = new HashMap<String, String>();
+
+  private String packagePrefix;
+  private final List<Scope> scopes = new ArrayList<Scope>();
+  private final Writer out;
+
+  /**
+   * @param out the stream to which Java source will be written. This should be
+   *     a buffered stream.
+   */
+  public JavaWriter(Writer out) {
+    this.out = out;
+  }
+
+  /**
+   * Emit a package declaration.
+   */
+  public void addPackage(String packageName) throws IOException {
+    if (this.packagePrefix != null) {
+      throw new IllegalStateException();
+    }
+    out.write("package ");
+    out.write(packageName);
+    out.write(";\n");
+    this.packagePrefix = packageName + ".";
+  }
+
+  /**
+   * Equivalent to {@code addImport(type.getName())}.
+   */
+  public void addImport(Class<?> type) throws IOException {
+    addImport(type.getName());
+  }
+
+  /**
+   * Emit an import for {@code type}. For the duration of the file, all
+   * references to this class will be automatically shortened.
+   */
+  public void addImport(String type) throws IOException {
+    Matcher matcher = TYPE_PATTERN.matcher(type);
+    if (!matcher.matches()) {
+      throw new IllegalArgumentException(type);
+    }
+    if (importedTypes.put(type, matcher.group(1)) != null) {
+      throw new IllegalArgumentException(type);
+    }
+    out.write("import ");
+    out.write(type);
+    out.write(";\n");
+  }
+
+  /**
+   * Emits a name like {@code java.lang.String} or {@code
+   * java.util.List<java.lang.String>}, shorting it with imports if
+   * possible.
+   */
+  private void type(String type) throws IOException {
+    if (this.packagePrefix == null) {
+      throw new IllegalStateException();
+    }
+
+    Matcher m = TYPE_PATTERN.matcher(type);
+    int pos = 0;
+    while (true) {
+      boolean found = m.find(pos);
+
+      // copy non-matching characters like "<"
+      int typeStart = found ? m.start() : type.length();
+      out.write(type, pos, typeStart - pos);
+
+      if (!found) {
+        break;
+      }
+
+      // copy a single class name, shortening it if possible
+      String name = m.group(0);
+      String imported;
+      if ((imported = importedTypes.get(name)) != null) {
+        out.write(imported);
+      } else if (name.startsWith(packagePrefix)
+          && name.indexOf('.', packagePrefix.length()) == -1) {
+        out.write(name.substring(packagePrefix.length()));
+      } else if (name.startsWith("java.lang.")) {
+        out.write(name.substring("java.lang.".length()));
+      } else {
+        out.write(name);
+      }
+      pos = m.end();
+    }
+  }
+
+  /**
+   * Emits a type declaration.
+   *
+   * @param kind such as "class", "interface" or "enum".
+   */
+  public void beginType(String type, String kind, int modifiers) throws IOException {
+    beginType(type, kind, modifiers, null);
+  }
+
+  /**
+   * Emits a type declaration.
+   *
+   * @param kind such as "class", "interface" or "enum".
+   * @param extendsType the class to extend, or null for no extends clause.
+   */
+  public void beginType(String type, String kind, int modifiers,
+      String extendsType, String... implementsTypes) throws IOException {
+    indent();
+    modifiers(modifiers);
+    out.write(kind);
+    out.write(" ");
+    type(type);
+    if (extendsType != null) {
+      out.write("\n");
+      indent();
+      out.write("    extends ");
+      type(extendsType);
+    }
+    if (implementsTypes.length > 0) {
+      out.write("\n");
+      indent();
+      out.write("    implements ");
+      for (int i = 0; i < implementsTypes.length; i++) {
+        if (i != 0) {
+          out.write(", ");
+        }
+        type(implementsTypes[i]);
+      }
+    }
+    out.write(" {\n");
+    pushScope(Scope.TYPE_DECLARATION);
+  }
+
+  /**
+   * Completes the current type declaration.
+   */
+  public void endType() throws IOException {
+    if (popScope() != Scope.TYPE_DECLARATION) {
+      throw new IllegalStateException();
+    }
+    indent();
+    out.write("}\n");
+  }
+
+  /**
+   * Emits a field declaration.
+   */
+  public void field(String type, String name, int modifiers) throws IOException {
+    field(type, name, modifiers, null);
+  }
+
+  public void field(String type, String name, int modifiers, String initialValue)
+      throws IOException {
+    indent();
+    modifiers(modifiers);
+    type(type);
+    out.write(" ");
+    out.write(name);
+
+    if (initialValue != null) {
+      out.write(" = ");
+      out.write(initialValue);
+    }
+    out.write(";\n");
+  }
+
+  /**
+   * Emit a method declaration.
+   *
+   * @param returnType the method's return type, or null for constructors.
+   * @param parameters alternating parameter types and names.
+   * @param name the method name, or the fully qualified class name for
+   *     constructors.
+   */
+  public void beginMethod(String returnType, String name, int modifiers, String... parameters)
+      throws IOException {
+    indent();
+    modifiers(modifiers);
+    if (returnType != null) {
+      type(returnType);
+      out.write(" ");
+      out.write(name);
+    } else {
+      type(name);
+    }
+    out.write("(");
+    for (int p = 0; p < parameters.length; ) {
+      if (p != 0) {
+        out.write(", ");
+      }
+      type(parameters[p++]);
+      out.write(" ");
+      type(parameters[p++]);
+    }
+    out.write(")");
+    if ((modifiers & Modifier.ABSTRACT) != 0) {
+      out.write(";\n");
+      pushScope(Scope.ABSTRACT_METHOD);
+    } else {
+      out.write(" {\n");
+      pushScope(Scope.NON_ABSTRACT_METHOD);
+    }
+  }
+
+  /**
+   * Annotates the next element with {@code annotation}. The annotation has no
+   * attributes.
+   */
+  public void annotation(String annotation) throws IOException {
+    indent();
+    out.write("@");
+    type(annotation);
+    out.write("\n");
+  }
+
+  /**
+   * Equivalent to {@code annotation(annotationType.getName())}.
+   */
+  public void annotation(Class<? extends Annotation> annotationType) throws IOException {
+    annotation(annotationType.getName());
+  }
+
+  /**
+   * @param pattern a code pattern like "int i = %s". Shouldn't contain a
+   * trailing semicolon or newline character.
+   */
+  public void statement(String pattern, Object... args) throws IOException {
+    checkInMethod();
+    indent();
+    out.write(String.format(pattern, args));
+    out.write(";\n");
+  }
+
+  /**
+   * @param controlFlow the control flow construct and its code, such as
+   *     "if (foo == 5)". Shouldn't contain braces or newline characters.
+   */
+  public void beginControlFlow(String controlFlow) throws IOException {
+    checkInMethod();
+    indent();
+    out.write(controlFlow);
+    out.write(" {\n");
+    pushScope(Scope.CONTROL_FLOW);
+  }
+
+  /**
+   * @param controlFlow the control flow construct and its code, such as
+   *     "else if (foo == 10)". Shouldn't contain braces or newline characters.
+   */
+  public void nextControlFlow(String controlFlow) throws IOException {
+    if (popScope() != Scope.CONTROL_FLOW) {
+      throw new IllegalArgumentException();
+    }
+
+    indent();
+    pushScope(Scope.CONTROL_FLOW);
+    out.write("} ");
+    out.write(controlFlow);
+    out.write(" {\n");
+  }
+
+  public void endControlFlow() throws IOException {
+    endControlFlow(null);
+  }
+
+  /**
+   * @param controlFlow the optional control flow construct and its code, such
+   *     as "while(foo == 20)". Only used for "do/while" control flows.
+   */
+  public void endControlFlow(String controlFlow) throws IOException {
+    if (popScope() != Scope.CONTROL_FLOW) {
+      throw new IllegalArgumentException();
+    }
+
+    indent();
+    if (controlFlow != null) {
+      out.write("} ");
+      out.write(controlFlow);
+      out.write(";\n");
+    } else {
+      out.write("}\n");
+    }
+  }
+
+  /**
+   * Completes the current method declaration.
+   */
+  public void endMethod() throws IOException {
+    Scope popped = popScope();
+    if (popped == Scope.NON_ABSTRACT_METHOD) {
+      indent();
+      out.write("}\n");
+    } else if (popped != Scope.ABSTRACT_METHOD) {
+      throw new IllegalStateException();
+    }
+  }
+
+  /**
+   * Returns the string literal representing {@code data}, including wrapping
+   * quotes.
+   */
+  public static String stringLiteral(String data) {
+    StringBuilder result = new StringBuilder();
+    result.append('"');
+    for (int i = 0; i < data.length(); i++) {
+      char c = data.charAt(i);
+      switch (c) {
+        case '"':
+          result.append("\\\"");
+          break;
+        case '\\':
+          result.append("\\\\");
+          break;
+        case '\t':
+          result.append("\\\t");
+          break;
+        case '\b':
+          result.append("\\\b");
+          break;
+        case '\n':
+          result.append("\\\n");
+          break;
+        case '\r':
+          result.append("\\\r");
+          break;
+        case '\f':
+          result.append("\\\f");
+          break;
+        default:
+          result.append(c);
+      }
+    }
+    result.append('"');
+    return result.toString();
+  }
+
+  public void close() throws IOException {
+    out.close();
+  }
+
+  /**
+   * Emit modifier names.
+   */
+  private void modifiers(int modifiers) throws IOException {
+    if ((modifiers & Modifier.PUBLIC) != 0) {
+      out.write("public ");
+    }
+    if ((modifiers & Modifier.PRIVATE) != 0) {
+      out.write("private ");
+    }
+    if ((modifiers & Modifier.PROTECTED) != 0) {
+      out.write("protected ");
+    }
+    if ((modifiers & Modifier.STATIC) != 0) {
+      out.write("static ");
+    }
+    if ((modifiers & Modifier.FINAL) != 0) {
+      out.write("final ");
+    }
+    if ((modifiers & Modifier.ABSTRACT) != 0) {
+      out.write("abstract ");
+    }
+    if ((modifiers & Modifier.SYNCHRONIZED) != 0) {
+      out.write("synchronized ");
+    }
+    if ((modifiers & Modifier.TRANSIENT) != 0) {
+      out.write("transient ");
+    }
+    if ((modifiers & Modifier.VOLATILE) != 0) {
+      out.write("volatile ");
+    }
+  }
+
+  private void indent() throws IOException {
+    for (int i = 0; i < scopes.size(); i++) {
+      out.write(INDENT);
+    }
+  }
+
+  private void checkInMethod() {
+    Scope scope = peekScope();
+    if (scope != Scope.NON_ABSTRACT_METHOD && scope != Scope.CONTROL_FLOW) {
+      throw new IllegalArgumentException();
+    }
+  }
+
+  private void pushScope(Scope pushed) {
+    scopes.add(pushed);
+  }
+
+  private Scope peekScope() {
+    return scopes.get(scopes.size() - 1);
+  }
+
+  private Scope popScope() {
+    return scopes.remove(scopes.size() - 1);
+  }
+
+  private enum Scope {
+    TYPE_DECLARATION,
+    ABSTRACT_METHOD,
+    NON_ABSTRACT_METHOD,
+    CONTROL_FLOW,
+  }
+}

gson/gson-codegen/src/main/resources/META-INF/services/javax.annotation.processing.Processor

@@ -0,0 +1 @@
+com.google.gson.codegen.GeneratedTypeAdapterProcessor