Java tutorial
package com.fasterxml.jackson.core.io; import java.io.*; import java.nio.ByteBuffer; import com.fasterxml.jackson.core.SerializableString; /** * String token that can lazily serialize String contained and then reuse that * serialization later on. This is similar to JDBC prepared statements, for example, * in that instances should only be created when they are used more than use; * prime candidates are various serializers. *<p> * Class is final for performance reasons and since this is not designed to * be extensible or customizable (customizations would occur in calling code) */ public class SerializedString implements SerializableString, java.io.Serializable { protected final String _value; /* 13-Dec-2010, tatu: Whether use volatile or not is actually an important * decision for multi-core use cases. Cost of volatility can be non-trivial * for heavy use cases, and serialized-string instances are accessed often. * Given that all code paths with common Jackson usage patterns go through * a few memory barriers (mostly with cache/reuse pool access) it seems safe * enough to omit volatiles here, given how simple lazy initialization is. * This can be compared to how {@link String#intern} works; lazily and * without synchronization or use of volatile keyword. */ protected /*volatile*/ byte[] _quotedUTF8Ref; protected /*volatile*/ byte[] _unquotedUTF8Ref; protected /*volatile*/ char[] _quotedChars; public SerializedString(String v) { if (v == null) { throw new IllegalStateException("Null String illegal for SerializedString"); } _value = v; } /* /********************************************************** /* Serializable overrides /********************************************************** */ /** * Ugly hack, to work through the requirement that _value is indeed final, * and that JDK serialization won't call ctor(s). * * @since 2.1 */ protected transient String _jdkSerializeValue; private void readObject(ObjectInputStream in) throws IOException { _jdkSerializeValue = in.readUTF(); } private void writeObject(ObjectOutputStream out) throws IOException { out.writeUTF(_value); } protected Object readResolve() { return new SerializedString(_jdkSerializeValue); } /* /********************************************************** /* API /********************************************************** */ @Override public final String getValue() { return _value; } /** * Returns length of the String as characters */ @Override public final int charLength() { return _value.length(); } @Override public final char[] asQuotedChars() { char[] result = _quotedChars; if (result == null) { result = JsonStringEncoder.getInstance().quoteAsString(_value); _quotedChars = result; } return result; } /** * Accessor for accessing value that has been quoted using JSON * quoting rules, and encoded using UTF-8 encoding. */ @Override public final byte[] asUnquotedUTF8() { byte[] result = _unquotedUTF8Ref; if (result == null) { result = JsonStringEncoder.getInstance().encodeAsUTF8(_value); _unquotedUTF8Ref = result; } return result; } /** * Accessor for accessing value as is (without JSON quoting) * encoded using UTF-8 encoding. */ @Override public final byte[] asQuotedUTF8() { byte[] result = _quotedUTF8Ref; if (result == null) { result = JsonStringEncoder.getInstance().quoteAsUTF8(_value); _quotedUTF8Ref = result; } return result; } /* /********************************************************** /* Additional 2.0 methods for appending/writing contents /********************************************************** */ @Override public int appendQuotedUTF8(byte[] buffer, int offset) { byte[] result = _quotedUTF8Ref; if (result == null) { result = JsonStringEncoder.getInstance().quoteAsUTF8(_value); _quotedUTF8Ref = result; } final int length = result.length; if ((offset + length) > buffer.length) { return -1; } System.arraycopy(result, 0, buffer, offset, length); return length; } @Override public int appendQuoted(char[] buffer, int offset) { char[] result = _quotedChars; if (result == null) { result = JsonStringEncoder.getInstance().quoteAsString(_value); _quotedChars = result; } final int length = result.length; if ((offset + length) > buffer.length) { return -1; } System.arraycopy(result, 0, buffer, offset, length); return length; } @Override public int appendUnquotedUTF8(byte[] buffer, int offset) { byte[] result = _unquotedUTF8Ref; if (result == null) { result = JsonStringEncoder.getInstance().encodeAsUTF8(_value); _unquotedUTF8Ref = result; } final int length = result.length; if ((offset + length) > buffer.length) { return -1; } System.arraycopy(result, 0, buffer, offset, length); return length; } @Override public int appendUnquoted(char[] buffer, int offset) { String str = _value; final int length = str.length(); if ((offset + length) > buffer.length) { return -1; } str.getChars(0, length, buffer, offset); return length; } @Override public int writeQuotedUTF8(OutputStream out) throws IOException { byte[] result = _quotedUTF8Ref; if (result == null) { result = JsonStringEncoder.getInstance().quoteAsUTF8(_value); _quotedUTF8Ref = result; } final int length = result.length; out.write(result, 0, length); return length; } @Override public int writeUnquotedUTF8(OutputStream out) throws IOException { byte[] result = _unquotedUTF8Ref; if (result == null) { result = JsonStringEncoder.getInstance().encodeAsUTF8(_value); _unquotedUTF8Ref = result; } final int length = result.length; out.write(result, 0, length); return length; } @Override public int putQuotedUTF8(ByteBuffer buffer) { byte[] result = _quotedUTF8Ref; if (result == null) { result = JsonStringEncoder.getInstance().quoteAsUTF8(_value); _quotedUTF8Ref = result; } final int length = result.length; if (length > buffer.remaining()) { return -1; } buffer.put(result, 0, length); return length; } @Override public int putUnquotedUTF8(ByteBuffer buffer) { byte[] result = _unquotedUTF8Ref; if (result == null) { result = JsonStringEncoder.getInstance().encodeAsUTF8(_value); _unquotedUTF8Ref = result; } final int length = result.length; if (length > buffer.remaining()) { return -1; } buffer.put(result, 0, length); return length; } /* /********************************************************** /* Standard method overrides /********************************************************** */ @Override public final String toString() { return _value; } @Override public final int hashCode() { return _value.hashCode(); } @Override public final boolean equals(Object o) { if (o == this) return true; if (o == null || o.getClass() != getClass()) return false; SerializedString other = (SerializedString) o; return _value.equals(other._value); } }