WireAdapter.java

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package org.glassfish.contextpropagation.wireadapters;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.HashMap;
import java.util.Map;

import org.glassfish.contextpropagation.SerializableContextFactory;
import org.glassfish.contextpropagation.bootstrap.LoggerAdapter.MessageID;
import org.glassfish.contextpropagation.internal.Entry;
import org.glassfish.contextpropagation.internal.Utils;

/**
 * Concrete WireAdapter instances define the methods for transforming
 * Entry's into serialized wire data and vice versa.
 * 
 * WireAdapters should thrive to:
 *  - encode data efficiently and compactly
 *  - be resilient to errors -- a problem decoding an entry should not cause the 
 *    decoding of subsequent entries to fail.
 */
public interface WireAdapter {
  static interface WireAdapterHelper {
    SerializableContextFactory findContextFactory(String contextName, String wireClassName);
    public void registerContextFactoryForContextNamed(String contextName, 
        String wireClassName, SerializableContextFactory factory);
    public void registerContextFactoryForClass(Class<?> contextClass, 
        String wireClassName, SerializableContextFactory factory);
  }
  public void prepareToWriteTo(OutputStream out) throws IOException;
  public <T> void write(String key, Entry entry) throws IOException;
  public void flush() throws IOException;
  public void prepareToReadFrom(InputStream is) throws IOException;
  public String readKey() throws IOException;
  public Entry readEntry() throws IOException, ClassNotFoundException;
  
  public static final WireAdapterHelper HELPER = new WireAdapterHelper() {   
    Map<String, SerializableContextFactory> contextFactoriesByContextName = new HashMap<String, SerializableContextFactory>();
    Map<String, String> wireClassNameByContextName = new HashMap<String, String>();
    public void registerContextFactoryForContextNamed(String contextName, 
        String wireClassName, SerializableContextFactory factory) {
      Utils.validateFactoryRegistrationArgs("contextName", 
          MessageID.WARN_FACTORY_ALREADY_REGISTERED_FOR_NAME, contextName, 
          factory, contextFactoriesByContextName);
      contextFactoriesByContextName.put(contextName, factory);
      wireClassNameByContextName.put(contextName, wireClassName);
    }

    Map<String, SerializableContextFactory> contextFactoriesByClassName = new HashMap<String, SerializableContextFactory>();
    Map<String, String> wireClassNameByClassName = new HashMap<String, String>();
    public void registerContextFactoryForClass(Class<?> contextClass, 
        String wireClassName, SerializableContextFactory factory) {
      Utils.validateFactoryRegistrationArgs("Context class name", 
          MessageID.WARN_FACTORY_ALREADY_REGISTERED_FOR_CLASS, 
          contextClass.getName(), factory, contextFactoriesByClassName);
      contextFactoriesByClassName.put(wireClassName, factory);
      wireClassNameByClassName.put(contextClass.getName(), wireClassName);
    }

    @Override
    public SerializableContextFactory findContextFactory(String contextName,
        String wireClassName) {
      SerializableContextFactory factory = contextFactoriesByClassName.get(wireClassName);
      if (factory == null) {
        factory = contextFactoriesByContextName.get(contextName);
      }
      return factory;
    }
  };
}