New streaming writer writes to DOMs

gson/src/main/java/com/google/gson/internal/bind/JsonElementWriter.java

@@ -0,0 +1,166 @@
+/*
+ * Copyright (C) 2011 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.internal.bind;
+
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonNull;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonPrimitive;
+import com.google.gson.stream.JsonWriter;
+import java.io.IOException;
+import java.io.Writer;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * This writer writes a JsonElement.
+ */
+public final class JsonElementWriter extends JsonWriter {
+  private static final Writer UNWRITABLE_WRITER = new Writer() {
+    @Override public void write(char[] buffer, int offset, int counter) {
+      throw new AssertionError();
+    }
+    @Override public void flush() throws IOException {
+      throw new AssertionError();
+    }
+    @Override public void close() throws IOException {
+      throw new AssertionError();
+    }
+  };
+
+  private final List<JsonElement> stack = new ArrayList<JsonElement>();
+  private String pendingName;
+
+  public JsonElementWriter() {
+    super(UNWRITABLE_WRITER);
+  }
+
+  public JsonElement get() {
+    if (stack.size() != 1) {
+      throw new IllegalStateException();
+    }
+    return stack.get(0);
+  }
+
+  private JsonElement peek() {
+    return stack.get(stack.size() - 1);
+  }
+
+  private void put(JsonElement value) {
+    if (pendingName != null) {
+      JsonObject object = (JsonObject) peek();
+      object.add(pendingName, value);
+      pendingName = null;
+    } else if (stack.isEmpty()) {
+      stack.add(value);
+    } else {
+      JsonElement element = peek();
+      if (element instanceof JsonArray) {
+        ((JsonArray) element).add(value);
+      } else {
+        throw new IllegalStateException();
+      }
+    }
+  }
+
+  @Override public JsonWriter beginArray() throws IOException {
+    JsonArray array = new JsonArray();
+    put(array);
+    stack.add(array);
+    return this;
+  }
+
+  @Override public JsonWriter endArray() throws IOException {
+    if (stack.isEmpty() || pendingName != null) {
+      throw new IllegalStateException();
+    }
+    JsonElement element = peek();
+    if (element instanceof JsonArray) {
+      stack.remove(stack.size() - 1);
+      return this;
+    }
+    throw new IllegalStateException();
+  }
+
+  @Override public JsonWriter beginObject() throws IOException {
+    JsonObject object = new JsonObject();
+    put(object);
+    stack.add(object);
+    return this;
+  }
+
+  @Override public JsonWriter endObject() throws IOException {
+    if (stack.isEmpty() || pendingName != null) {
+      throw new IllegalStateException();
+    }
+    JsonElement element = peek();
+    if (element instanceof JsonObject) {
+      stack.remove(stack.size() - 1);
+      return this;
+    }
+    throw new IllegalStateException();
+  }
+
+  @Override public JsonWriter name(String name) throws IOException {
+    if (stack.isEmpty() || pendingName != null) {
+      throw new IllegalStateException();
+    }
+    JsonElement element = peek();
+    if (element instanceof JsonObject) {
+      pendingName = name;
+      return this;
+    }
+    throw new IllegalStateException();
+  }
+
+  @Override public JsonWriter value(String value) throws IOException {
+    put(new JsonPrimitive(value));
+    return this;
+  }
+
+  @Override public JsonWriter nullValue() throws IOException {
+    put(JsonNull.INSTANCE);
+    return this;
+  }
+
+  @Override public JsonWriter value(boolean value) throws IOException {
+    put(new JsonPrimitive(value));
+    return this;
+  }
+
+  @Override public JsonWriter value(double value) throws IOException {
+    put(new JsonPrimitive(value));
+    return this;
+  }
+
+  @Override public JsonWriter value(long value) throws IOException {
+    put(new JsonPrimitive(value));
+    return this;
+  }
+
+  @Override public JsonWriter value(Number value) throws IOException {
+    put(new JsonPrimitive(value));
+    return this;
+  }
+
+  @Override public void flush() throws IOException {
+  }
+
+  @Override public void close() throws IOException {
+  }
+}

gson/src/main/java/com/google/gson/stream/JsonWriter.java

@@ -120,7 +120,7 @@ import java.util.List;
  * @author Jesse Wilson
  * @since 1.6
  */
-public final class JsonWriter implements Closeable {
+public class JsonWriter implements Closeable {
 
   /** The output data, containing at most one top-level array or object. */
   private final Writer out;
@@ -165,7 +165,7 @@ public final class JsonWriter implements Closeable {
    *
    * @param indent a string containing only whitespace.
    */
-  public void setIndent(String indent) {
+  public final void setIndent(String indent) {
     if (indent.length() == 0) {
       this.indent = null;
       this.separator = ":";
@@ -187,7 +187,7 @@ public final class JsonWriter implements Closeable {
    *       Double#isInfinite() infinities}.
    * </ul>
    */
-  public void setLenient(boolean lenient) {
+  public final void setLenient(boolean lenient) {
     this.lenient = lenient;
   }
 
@@ -205,7 +205,7 @@ public final class JsonWriter implements Closeable {
    * setting, your XML/HTML encoder should replace these characters with the
    * corresponding escape sequences.
    */
-  public void setHtmlSafe(boolean htmlSafe) {
+  public final void setHtmlSafe(boolean htmlSafe) {
     this.htmlSafe = htmlSafe;
   }
 
@@ -213,7 +213,7 @@ public final class JsonWriter implements Closeable {
    * Returns true if this writer writes JSON that's safe for inclusion in HTML
    * and XML documents.
    */
-  public boolean isHtmlSafe() {
+  public final boolean isHtmlSafe() {
     return htmlSafe;
   }
 

gson/src/test/java/com/google/gson/internal/bind/JsonElementWriterTest.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2011 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.internal.bind;
+
+import java.io.IOException;
+import junit.framework.TestCase;
+
+public final class JsonElementWriterTest extends TestCase {
+
+  // TODO: more tests
+  // TODO: close support
+
+  public void testArray() throws IOException {
+    JsonElementWriter writer = new JsonElementWriter();
+    writer.beginArray();
+    writer.value(1);
+    writer.value(2);
+    writer.value(3);
+    writer.endArray();
+    assertEquals("[1,2,3]", writer.get().toString());
+  }
+
+  public void testNestedArray() throws IOException {
+    JsonElementWriter writer = new JsonElementWriter();
+    writer.beginArray();
+    writer.beginArray();
+    writer.endArray();
+    writer.beginArray();
+    writer.beginArray();
+    writer.endArray();
+    writer.endArray();
+    writer.endArray();
+    assertEquals("[[],[[]]]", writer.get().toString());
+  }
+
+  public void testObject() throws IOException {
+    JsonElementWriter writer = new JsonElementWriter();
+    writer.beginObject();
+    writer.name("A").value(1);
+    writer.name("B").value(2);
+    writer.endObject();
+    assertEquals("{\"A\":1,\"B\":2}", writer.get().toString());
+  }
+
+  public void testNestedObject() throws IOException {
+    JsonElementWriter writer = new JsonElementWriter();
+    writer.beginObject();
+    writer.name("A");
+    writer.beginObject();
+    writer.name("B");
+    writer.beginObject();
+    writer.endObject();
+    writer.endObject();
+    writer.name("C");
+    writer.beginObject();
+    writer.endObject();
+    writer.endObject();
+    assertEquals("{\"A\":{\"B\":{}},\"C\":{}}", writer.get().toString());
+  }
+}