Java tutorial
/* * 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.thrift.protocol; import java.nio.ByteBuffer; import java.nio.charset.StandardCharsets; import java.util.Stack; import org.apache.thrift.TException; import org.apache.thrift.transport.TTransport; /** * JSON protocol implementation for thrift. * * This protocol is write-only and produces a simple output format * suitable for parsing by scripting languages. It should not be * confused with the full-featured TJSONProtocol. * */ public class TSimpleJSONProtocol extends TProtocol { /** * Factory */ public static class Factory implements TProtocolFactory { public TProtocol getProtocol(TTransport trans) { return new TSimpleJSONProtocol(trans); } } private static final byte[] COMMA = new byte[] { ',' }; private static final byte[] COLON = new byte[] { ':' }; private static final byte[] LBRACE = new byte[] { '{' }; private static final byte[] RBRACE = new byte[] { '}' }; private static final byte[] LBRACKET = new byte[] { '[' }; private static final byte[] RBRACKET = new byte[] { ']' }; private static final char QUOTE = '"'; private static final TStruct ANONYMOUS_STRUCT = new TStruct(); private static final TField ANONYMOUS_FIELD = new TField(); private static final TMessage EMPTY_MESSAGE = new TMessage(); private static final TSet EMPTY_SET = new TSet(); private static final TList EMPTY_LIST = new TList(); private static final TMap EMPTY_MAP = new TMap(); private static final String LIST = "list"; private static final String SET = "set"; private static final String MAP = "map"; protected class Context { protected void write() throws TException { } /** * Returns whether the current value is a key in a map */ protected boolean isMapKey() { return false; } } protected class ListContext extends Context { protected boolean first_ = true; protected void write() throws TException { if (first_) { first_ = false; } else { trans_.write(COMMA); } } } protected class StructContext extends Context { protected boolean first_ = true; protected boolean colon_ = true; protected void write() throws TException { if (first_) { first_ = false; colon_ = true; } else { trans_.write(colon_ ? COLON : COMMA); colon_ = !colon_; } } } protected class MapContext extends StructContext { protected boolean isKey = true; @Override protected void write() throws TException { super.write(); isKey = !isKey; } protected boolean isMapKey() { // we want to coerce map keys to json strings regardless // of their type return isKey; } } protected final Context BASE_CONTEXT = new Context(); /** * Stack of nested contexts that we may be in. */ protected Stack<Context> writeContextStack_ = new Stack<Context>(); /** * Current context that we are in */ protected Context writeContext_ = BASE_CONTEXT; /** * Push a new write context onto the stack. */ protected void pushWriteContext(Context c) { writeContextStack_.push(writeContext_); writeContext_ = c; } /** * Pop the last write context off the stack */ protected void popWriteContext() { writeContext_ = writeContextStack_.pop(); } /** * Reset the write context stack to its initial state. */ protected void resetWriteContext() { while (!writeContextStack_.isEmpty()) { popWriteContext(); } } /** * Used to make sure that we are not encountering a map whose keys are containers */ protected void assertContextIsNotMapKey(String invalidKeyType) throws CollectionMapKeyException { if (writeContext_.isMapKey()) { throw new CollectionMapKeyException( "Cannot serialize a map with keys that are of type " + invalidKeyType); } } /** * Constructor */ public TSimpleJSONProtocol(TTransport trans) { super(trans); } @Override public void writeMessageBegin(TMessage message) throws TException { resetWriteContext(); // THRIFT-3743 trans_.write(LBRACKET); pushWriteContext(new ListContext()); writeString(message.name); writeByte(message.type); writeI32(message.seqid); } @Override public void writeMessageEnd() throws TException { popWriteContext(); trans_.write(RBRACKET); } @Override public void writeStructBegin(TStruct struct) throws TException { writeContext_.write(); trans_.write(LBRACE); pushWriteContext(new StructContext()); } @Override public void writeStructEnd() throws TException { popWriteContext(); trans_.write(RBRACE); } @Override public void writeFieldBegin(TField field) throws TException { // Note that extra type information is omitted in JSON! writeString(field.name); } @Override public void writeFieldEnd() throws TException { } @Override public void writeFieldStop() throws TException { } @Override public void writeMapBegin(TMap map) throws TException { assertContextIsNotMapKey(MAP); writeContext_.write(); trans_.write(LBRACE); pushWriteContext(new MapContext()); // No metadata! } @Override public void writeMapEnd() throws TException { popWriteContext(); trans_.write(RBRACE); } @Override public void writeListBegin(TList list) throws TException { assertContextIsNotMapKey(LIST); writeContext_.write(); trans_.write(LBRACKET); pushWriteContext(new ListContext()); // No metadata! } @Override public void writeListEnd() throws TException { popWriteContext(); trans_.write(RBRACKET); } @Override public void writeSetBegin(TSet set) throws TException { assertContextIsNotMapKey(SET); writeContext_.write(); trans_.write(LBRACKET); pushWriteContext(new ListContext()); // No metadata! } @Override public void writeSetEnd() throws TException { popWriteContext(); trans_.write(RBRACKET); } @Override public void writeBool(boolean b) throws TException { writeByte(b ? (byte) 1 : (byte) 0); } @Override public void writeByte(byte b) throws TException { writeI32(b); } @Override public void writeI16(short i16) throws TException { writeI32(i16); } @Override public void writeI32(int i32) throws TException { if (writeContext_.isMapKey()) { writeString(Integer.toString(i32)); } else { writeContext_.write(); _writeStringData(Integer.toString(i32)); } } public void _writeStringData(String s) throws TException { byte[] b = s.getBytes(StandardCharsets.UTF_8); trans_.write(b); } @Override public void writeI64(long i64) throws TException { if (writeContext_.isMapKey()) { writeString(Long.toString(i64)); } else { writeContext_.write(); _writeStringData(Long.toString(i64)); } } @Override public void writeDouble(double dub) throws TException { if (writeContext_.isMapKey()) { writeString(Double.toString(dub)); } else { writeContext_.write(); _writeStringData(Double.toString(dub)); } } @Override public void writeString(String str) throws TException { writeContext_.write(); int length = str.length(); StringBuffer escape = new StringBuffer(length + 16); escape.append(QUOTE); for (int i = 0; i < length; ++i) { char c = str.charAt(i); switch (c) { case '"': case '\\': escape.append('\\'); escape.append(c); break; case '\b': escape.append('\\'); escape.append('b'); break; case '\f': escape.append('\\'); escape.append('f'); break; case '\n': escape.append('\\'); escape.append('n'); break; case '\r': escape.append('\\'); escape.append('r'); break; case '\t': escape.append('\\'); escape.append('t'); break; default: // Control characters! According to JSON RFC u0020 (space) if (c < ' ') { String hex = Integer.toHexString(c); escape.append('\\'); escape.append('u'); for (int j = 4; j > hex.length(); --j) { escape.append('0'); } escape.append(hex); } else { escape.append(c); } break; } } escape.append(QUOTE); _writeStringData(escape.toString()); } @Override public void writeBinary(ByteBuffer bin) throws TException { // TODO(mcslee): Fix this writeString(new String(bin.array(), bin.position() + bin.arrayOffset(), bin.limit() - bin.position() - bin.arrayOffset(), StandardCharsets.UTF_8)); } /** * Reading methods. */ @Override public TMessage readMessageBegin() throws TException { // TODO(mcslee): implement return EMPTY_MESSAGE; } @Override public void readMessageEnd() throws TException { } @Override public TStruct readStructBegin() throws TException { // TODO(mcslee): implement return ANONYMOUS_STRUCT; } @Override public void readStructEnd() throws TException { } @Override public TField readFieldBegin() throws TException { // TODO(mcslee): implement return ANONYMOUS_FIELD; } @Override public void readFieldEnd() throws TException { } @Override public TMap readMapBegin() throws TException { // TODO(mcslee): implement return EMPTY_MAP; } @Override public void readMapEnd() throws TException { } @Override public TList readListBegin() throws TException { // TODO(mcslee): implement return EMPTY_LIST; } @Override public void readListEnd() throws TException { } @Override public TSet readSetBegin() throws TException { // TODO(mcslee): implement return EMPTY_SET; } @Override public void readSetEnd() throws TException { } @Override public boolean readBool() throws TException { return (readByte() == 1); } @Override public byte readByte() throws TException { // TODO(mcslee): implement return 0; } @Override public short readI16() throws TException { // TODO(mcslee): implement return 0; } @Override public int readI32() throws TException { // TODO(mcslee): implement return 0; } @Override public long readI64() throws TException { // TODO(mcslee): implement return 0; } @Override public double readDouble() throws TException { // TODO(mcslee): implement return 0; } @Override public String readString() throws TException { // TODO(mcslee): implement return ""; } public String readStringBody(int size) throws TException { // TODO(mcslee): implement return ""; } @Override public ByteBuffer readBinary() throws TException { // TODO(mcslee): implement return ByteBuffer.wrap(new byte[0]); } public static class CollectionMapKeyException extends TException { public CollectionMapKeyException(String message) { super(message); } } }