Package org.apache.hadoop.io

Class ObjectWritable

java.lang.Object
org.apache.hadoop.io.ObjectWritable
All Implemented Interfaces:
Configurable, Writable
@Public @Stable public class ObjectWritable extends Object implements Writable, Configurable
A polymorphic Writable that writes an instance with it's class name. Handles arrays, strings and primitive types without a Writable wrapper.

  • Constructor Details

    • ObjectWritable

      public ObjectWritable()

    • ObjectWritable

      public ObjectWritable(Object instance)

    • ObjectWritable

      public ObjectWritable(Class declaredClass, Object instance)

  • Method Details

    • get

      public Object get()
      Return the instance, or null if none.
      Returns:
      the instance, or null if none.

    • getDeclaredClass

      public Class getDeclaredClass()
      Return the class this is meant to be.
      Returns:
      the class this is meant to be.

    • set

      public void set(Object instance)
      Reset the instance.
      Parameters:
      instance - instance.

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • readFields

      public void readFields(DataInput in) throws IOException
      Description copied from interface: Writable
      Deserialize the fields of this object from in.

      For efficiency, implementations should attempt to re-use storage in the existing object where possible.

      Specified by:
      readFields in interface Writable
      Parameters:
      in - DataInput to deseriablize this object from.
      Throws:
      IOException - any other problem for readFields.

    • write

      public void write(DataOutput out) throws IOException
      Description copied from interface: Writable
      Serialize the fields of this object to out.
      Specified by:
      write in interface Writable
      Parameters:
      out - DataOuput to serialize this object into.
      Throws:
      IOException - any other problem for write.

    • writeObject

      public static void writeObject(DataOutput out, Object instance, Class declaredClass, Configuration conf) throws IOException
      Write a Writable, String, primitive type, or an array of the preceding.
      Parameters:
      out - DataOutput.
      instance - instance.
      conf - Configuration.
      declaredClass - declaredClass.
      Throws:
      IOException - raised on errors performing I/O.

    • writeObject

      public static void writeObject(DataOutput out, Object instance, Class declaredClass, Configuration conf, boolean allowCompactArrays) throws IOException
      Write a Writable, String, primitive type, or an array of the preceding.
      Parameters:
      allowCompactArrays - - set true for RPC and internal or intra-cluster usages. Set false for inter-cluster, File, and other persisted output usages, to preserve the ability to interchange files with other clusters that may not be running the same version of software. Sometime in ~2013 we can consider removing this parameter and always using the compact format.
      conf - configuration.
      out - dataoutput.
      declaredClass - declaredClass.
      instance - instance.
      Throws:
      IOException - raised on errors performing I/O.

    • readObject

      public static Object readObject(DataInput in, Configuration conf) throws IOException
      Read a Writable, String, primitive type, or an array of the preceding.
      Parameters:
      conf - configuration.
      in - DataInput.
      Returns:
      Object.
      Throws:
      IOException - raised on errors performing I/O.

    • readObject

      public static Object readObject(DataInput in, ObjectWritable objectWritable, Configuration conf) throws IOException
      Read a Writable, String, primitive type, or an array of the preceding.
      Parameters:
      in - DataInput.
      objectWritable - objectWritable.
      conf - configuration.
      Returns:
      Object.
      Throws:
      IOException - raised on errors performing I/O.

    • loadClass

      public static Class<?> loadClass(Configuration conf, String className)
      Find and load the class with given name className by first finding it in the specified conf. If the specified conf is null, try load it directly.
      Parameters:
      conf - configuration.
      className - classname.
      Returns:
      Class.

    • setConf

      public void setConf(Configuration conf)
      Description copied from interface: Configurable
      Set the configuration to be used by this object.
      Specified by:
      setConf in interface Configurable
      Parameters:
      conf - configuration to be used

    • getConf

      public Configuration getConf()
      Description copied from interface: Configurable
      Return the configuration used by this object.
      Specified by:
      getConf in interface Configurable
      Returns:
      Configuration