ObjectWritable.java
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上传日期:2018-01-08
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文件大小:9k
- /**
- * Licensed to the Apache Software Foundation (ASF) under one
- * or more contributor license agreements. See the NOTICE file
- * distributed with this work for additional information
- * regarding copyright ownership. The ASF licenses this file
- * to you 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 org.apache.hadoop.io;
- import java.lang.reflect.Array;
- import java.io.*;
- import java.util.*;
- import org.apache.hadoop.conf.*;
- /** A polymorphic Writable that writes an instance with it's class name.
- * Handles arrays, strings and primitive types without a Writable wrapper.
- */
- public class ObjectWritable implements Writable, Configurable {
- private Class declaredClass;
- private Object instance;
- private Configuration conf;
- public ObjectWritable() {}
-
- public ObjectWritable(Object instance) {
- set(instance);
- }
- public ObjectWritable(Class declaredClass, Object instance) {
- this.declaredClass = declaredClass;
- this.instance = instance;
- }
- /** Return the instance, or null if none. */
- public Object get() { return instance; }
-
- /** Return the class this is meant to be. */
- public Class getDeclaredClass() { return declaredClass; }
-
- /** Reset the instance. */
- public void set(Object instance) {
- this.declaredClass = instance.getClass();
- this.instance = instance;
- }
-
- public String toString() {
- return "OW[class=" + declaredClass + ",value=" + instance + "]";
- }
-
- public void readFields(DataInput in) throws IOException {
- readObject(in, this, this.conf);
- }
-
- public void write(DataOutput out) throws IOException {
- writeObject(out, instance, declaredClass, conf);
- }
- private static final Map<String, Class<?>> PRIMITIVE_NAMES = new HashMap<String, Class<?>>();
- static {
- PRIMITIVE_NAMES.put("boolean", Boolean.TYPE);
- PRIMITIVE_NAMES.put("byte", Byte.TYPE);
- PRIMITIVE_NAMES.put("char", Character.TYPE);
- PRIMITIVE_NAMES.put("short", Short.TYPE);
- PRIMITIVE_NAMES.put("int", Integer.TYPE);
- PRIMITIVE_NAMES.put("long", Long.TYPE);
- PRIMITIVE_NAMES.put("float", Float.TYPE);
- PRIMITIVE_NAMES.put("double", Double.TYPE);
- PRIMITIVE_NAMES.put("void", Void.TYPE);
- }
- private static class NullInstance extends Configured implements Writable {
- private Class<?> declaredClass;
- public NullInstance() { super(null); }
- public NullInstance(Class declaredClass, Configuration conf) {
- super(conf);
- this.declaredClass = declaredClass;
- }
- public void readFields(DataInput in) throws IOException {
- String className = UTF8.readString(in);
- declaredClass = PRIMITIVE_NAMES.get(className);
- if (declaredClass == null) {
- try {
- declaredClass = getConf().getClassByName(className);
- } catch (ClassNotFoundException e) {
- throw new RuntimeException(e.toString());
- }
- }
- }
- public void write(DataOutput out) throws IOException {
- UTF8.writeString(out, declaredClass.getName());
- }
- }
- /** Write a {@link Writable}, {@link String}, primitive type, or an array of
- * the preceding. */
- public static void writeObject(DataOutput out, Object instance,
- Class declaredClass,
- Configuration conf) throws IOException {
- if (instance == null) { // null
- instance = new NullInstance(declaredClass, conf);
- declaredClass = Writable.class;
- }
- UTF8.writeString(out, declaredClass.getName()); // always write declared
- if (declaredClass.isArray()) { // array
- int length = Array.getLength(instance);
- out.writeInt(length);
- for (int i = 0; i < length; i++) {
- writeObject(out, Array.get(instance, i),
- declaredClass.getComponentType(), conf);
- }
-
- } else if (declaredClass == String.class) { // String
- UTF8.writeString(out, (String)instance);
-
- } else if (declaredClass.isPrimitive()) { // primitive type
- if (declaredClass == Boolean.TYPE) { // boolean
- out.writeBoolean(((Boolean)instance).booleanValue());
- } else if (declaredClass == Character.TYPE) { // char
- out.writeChar(((Character)instance).charValue());
- } else if (declaredClass == Byte.TYPE) { // byte
- out.writeByte(((Byte)instance).byteValue());
- } else if (declaredClass == Short.TYPE) { // short
- out.writeShort(((Short)instance).shortValue());
- } else if (declaredClass == Integer.TYPE) { // int
- out.writeInt(((Integer)instance).intValue());
- } else if (declaredClass == Long.TYPE) { // long
- out.writeLong(((Long)instance).longValue());
- } else if (declaredClass == Float.TYPE) { // float
- out.writeFloat(((Float)instance).floatValue());
- } else if (declaredClass == Double.TYPE) { // double
- out.writeDouble(((Double)instance).doubleValue());
- } else if (declaredClass == Void.TYPE) { // void
- } else {
- throw new IllegalArgumentException("Not a primitive: "+declaredClass);
- }
- } else if (declaredClass.isEnum()) { // enum
- UTF8.writeString(out, ((Enum)instance).name());
- } else if (Writable.class.isAssignableFrom(declaredClass)) { // Writable
- UTF8.writeString(out, instance.getClass().getName());
- ((Writable)instance).write(out);
- } else {
- throw new IOException("Can't write: "+instance+" as "+declaredClass);
- }
- }
-
-
- /** Read a {@link Writable}, {@link String}, primitive type, or an array of
- * the preceding. */
- public static Object readObject(DataInput in, Configuration conf)
- throws IOException {
- return readObject(in, null, conf);
- }
-
- /** Read a {@link Writable}, {@link String}, primitive type, or an array of
- * the preceding. */
- @SuppressWarnings("unchecked")
- public static Object readObject(DataInput in, ObjectWritable objectWritable, Configuration conf)
- throws IOException {
- String className = UTF8.readString(in);
- Class<?> declaredClass = PRIMITIVE_NAMES.get(className);
- if (declaredClass == null) {
- try {
- declaredClass = conf.getClassByName(className);
- } catch (ClassNotFoundException e) {
- throw new RuntimeException("readObject can't find class " + className, e);
- }
- }
- Object instance;
-
- if (declaredClass.isPrimitive()) { // primitive types
- if (declaredClass == Boolean.TYPE) { // boolean
- instance = Boolean.valueOf(in.readBoolean());
- } else if (declaredClass == Character.TYPE) { // char
- instance = Character.valueOf(in.readChar());
- } else if (declaredClass == Byte.TYPE) { // byte
- instance = Byte.valueOf(in.readByte());
- } else if (declaredClass == Short.TYPE) { // short
- instance = Short.valueOf(in.readShort());
- } else if (declaredClass == Integer.TYPE) { // int
- instance = Integer.valueOf(in.readInt());
- } else if (declaredClass == Long.TYPE) { // long
- instance = Long.valueOf(in.readLong());
- } else if (declaredClass == Float.TYPE) { // float
- instance = Float.valueOf(in.readFloat());
- } else if (declaredClass == Double.TYPE) { // double
- instance = Double.valueOf(in.readDouble());
- } else if (declaredClass == Void.TYPE) { // void
- instance = null;
- } else {
- throw new IllegalArgumentException("Not a primitive: "+declaredClass);
- }
- } else if (declaredClass.isArray()) { // array
- int length = in.readInt();
- instance = Array.newInstance(declaredClass.getComponentType(), length);
- for (int i = 0; i < length; i++) {
- Array.set(instance, i, readObject(in, conf));
- }
-
- } else if (declaredClass == String.class) { // String
- instance = UTF8.readString(in);
- } else if (declaredClass.isEnum()) { // enum
- instance = Enum.valueOf((Class<? extends Enum>) declaredClass, UTF8.readString(in));
- } else { // Writable
- Class instanceClass = null;
- String str = "";
- try {
- str = UTF8.readString(in);
- instanceClass = conf.getClassByName(str);
- } catch (ClassNotFoundException e) {
- throw new RuntimeException("readObject can't find class " + str, e);
- }
-
- Writable writable = WritableFactories.newInstance(instanceClass, conf);
- writable.readFields(in);
- instance = writable;
- if (instanceClass == NullInstance.class) { // null
- declaredClass = ((NullInstance)instance).declaredClass;
- instance = null;
- }
- }
- if (objectWritable != null) { // store values
- objectWritable.declaredClass = declaredClass;
- objectWritable.instance = instance;
- }
- return instance;
-
- }
- public void setConf(Configuration conf) {
- this.conf = conf;
- }
- public Configuration getConf() {
- return this.conf;
- }
-
- }