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/*
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* To change this template, choose Tools | Templates
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* and open the template in the editor.
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*/
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package org.apidesign.delegatingwriter;
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import java.io.BufferedWriter;
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import java.io.IOException;
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import java.io.Writer;
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/**
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* This is a regular {@link BufferedWriter}, just its implementation
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* of the append method can choose from three options. This allows us to
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* simulate the potential pros and cons of various possible implementations.
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*
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* @author Jaroslav Tulach <jaroslav.tulach@apidesign.org>
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*/
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public class AltBufferedWriter extends BufferedWriter {
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private final Writer out;
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private final Behaviour behaviour;
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public AltBufferedWriter(Writer out) {
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// behave exactly like BufferedWriter in 1.5 behaves
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this(out, Behaviour.DELEGATE_TO_SUPER);
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}
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public AltBufferedWriter(Writer out, Behaviour behaviour) {
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super(out);
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this.out = out;
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this.behaviour = behaviour;
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}
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@Override
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public Writer append(CharSequence csq) throws IOException {
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switch (behaviour) {
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case THROW_EXCEPTION: return appendThrowException(csq);
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case DELEGATE_TO_SUPER: return appendDelegateToSuper(csq);
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case DELEGATE_TO_OUT: return appendDelegateToUnderlaying(csq);
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case DELEGATE_CONDITIONALLY: return appendDelegateConditionally(csq);
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default: throw new IllegalStateException("Unknown" + behaviour);
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}
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}
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public Writer appendThrowException(CharSequence csq) throws IOException {
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/* in case of real code, this would be part of the regular append method BEGIN: writer.throw
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public Writer append(CharSequence csq) throws IOException {
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/* thrown an exception as this method is new and subclasses need to override it */
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throw new UnsupportedOperationException();
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}
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// END: writer.throw
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public Writer appendDelegateToSuper(CharSequence csq) throws IOException {
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// non-efficient variant of delegating via converting to String first
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// and using one of methods that existed in 1.4
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// BEGIN: writer.super
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if (csq == null) {
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write("null");
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} else {
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write(csq.toString());
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}
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return this;
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// END: writer.super
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}
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public Writer appendDelegateToUnderlaying(CharSequence csq) throws IOException {
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// BEGIN: writer.delegateout
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// efficient, yet dangerous delegation skipping methods unknown to
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// subclasses that used version 1.4
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if (csq != null && csq.length() < 1024) {
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write(csq.toString());
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} else {
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flush();
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out.append(csq);
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}
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return this;
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// END: writer.delegateout
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}
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private Writer appendDelegateConditionally(CharSequence csq) throws IOException {
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// BEGIN: writer.conditionally
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boolean isOverriden = false;
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try {
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isOverriden =
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(getClass().getMethod("write", String.class).getDeclaringClass() != Writer.class) ||
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(getClass().getMethod("write", Integer.TYPE).getDeclaringClass() != BufferedWriter.class) ||
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(getClass().getMethod("write", String.class, Integer.TYPE, Integer.TYPE).getDeclaringClass() != BufferedWriter.class);
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} catch (Exception ex) {
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throw new IOException(ex);
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}
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if (isOverriden || (csq != null && csq.length() < 1024)) {
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write(csq.toString());
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} else {
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flush();
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out.append(csq);
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}
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return this;
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// END: writer.conditionally
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}
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public enum Behaviour {
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THROW_EXCEPTION, DELEGATE_TO_SUPER, DELEGATE_TO_OUT, DELEGATE_CONDITIONALLY
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}
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}
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