Package org.apache.hadoop.util

Class JsonSerialization<T>

java.lang.Object
org.apache.hadoop.util.JsonSerialization<T>
Type Parameters:
T - Type to marshal.
@Private @Evolving public class JsonSerialization<T> extends Object
Support for marshalling objects to and from JSON. It constructs an object mapper as an instance field. and synchronizes access to those methods which use the mapper. This class was extracted from org.apache.hadoop.registry.client.binding.JsonSerDeser, which is now a subclass of this class.

  • Constructor Details

    • JsonSerialization

      public JsonSerialization(Class<T> classType, boolean failOnUnknownProperties, boolean pretty)
      Create an instance bound to a specific type.
      Parameters:
      classType - class to marshall
      failOnUnknownProperties - fail if an unknown property is encountered.
      pretty - generate pretty (indented) output?

  • Method Details

    • writer

      public static com.fasterxml.jackson.databind.ObjectWriter writer()
      Returns:
      an ObjectWriter which pretty-prints its output

    • mapReader

      public static com.fasterxml.jackson.databind.ObjectReader mapReader()
      Returns:
      an ObjectReader which returns simple Maps.

    • getName

      public String getName()
      Get the simple name of the class type to be marshalled.
      Returns:
      the name of the class being marshalled

    • getMapper

      public com.fasterxml.jackson.databind.ObjectMapper getMapper()
      Get the mapper of this class.
      Returns:
      the mapper

    • fromJson

      public T fromJson(String json) throws IOException, com.fasterxml.jackson.core.JsonParseException, com.fasterxml.jackson.databind.JsonMappingException
      Convert from JSON.
      Parameters:
      json - input
      Returns:
      the parsed JSON
      Throws:
      IOException - IO problems
      com.fasterxml.jackson.core.JsonParseException - If the input is not well-formatted
      com.fasterxml.jackson.databind.JsonMappingException - failure to map from the JSON to this class

    • fromJsonStream

      public T fromJsonStream(InputStream stream) throws IOException
      Read from an input stream.
      Parameters:
      stream - stream to read from
      Returns:
      the parsed entity
      Throws:
      IOException - IO problems
      com.fasterxml.jackson.core.JsonParseException - If the input is not well-formatted
      com.fasterxml.jackson.databind.JsonMappingException - failure to map from the JSON to this class

    • load

      public T load(File jsonFile) throws IOException, com.fasterxml.jackson.core.JsonParseException, com.fasterxml.jackson.databind.JsonMappingException
      Load from a JSON text file.
      Parameters:
      jsonFile - input file
      Returns:
      the parsed JSON
      Throws:
      IOException - IO problems
      com.fasterxml.jackson.core.JsonParseException - If the input is not well-formatted
      com.fasterxml.jackson.databind.JsonMappingException - failure to map from the JSON to this class

    • save

      public void save(File file, T instance) throws IOException
      Save to a local file. Any existing file is overwritten unless the OS blocks that.
      Parameters:
      file - file
      instance - instance
      Throws:
      IOException - IO exception

    • fromResource

      public T fromResource(String resource) throws IOException, com.fasterxml.jackson.core.JsonParseException, com.fasterxml.jackson.databind.JsonMappingException
      Convert from a JSON file.
      Parameters:
      resource - input file
      Returns:
      the parsed JSON
      Throws:
      IOException - IO problems
      com.fasterxml.jackson.core.JsonParseException - If the input is not well-formatted
      com.fasterxml.jackson.databind.JsonMappingException - failure to map from the JSON to this class

    • fromInstance

      public T fromInstance(T instance) throws IOException
      clone by converting to JSON and back again. This is much less efficient than any Java clone process.
      Parameters:
      instance - instance to duplicate
      Returns:
      a new instance
      Throws:
      IOException - IO problems.

    • load

      public T load(FileSystem fs, Path path) throws IOException
      Load from a Hadoop filesystem.
      Parameters:
      fs - filesystem
      path - path
      Returns:
      a loaded object
      Throws:
      PathIOException - JSON parse problem
      IOException - IO problems

    • load

      public T load(FileSystem fs, Path path, @Nullable FileStatus status) throws IOException
      Load from a Hadoop filesystem. If a file status is supplied, it's passed in to the openFile() call so that FS implementations can optimize their opening.
      Parameters:
      fs - filesystem
      path - path
      status - status of the file to open.
      Returns:
      a loaded object
      Throws:
      PathIOException - JSON parse problem
      EOFException - file status references an empty file
      IOException - IO problems

    • save

      public void save(FileSystem fs, Path path, T instance, boolean overwrite) throws IOException
      Save to a Hadoop filesystem.
      Parameters:
      fs - filesystem
      path - path
      overwrite - should any existing file be overwritten
      instance - instance
      Throws:
      IOException - IO exception.

    • writeJsonAsBytes

      public void writeJsonAsBytes(T instance, OutputStream dataOutputStream) throws IOException
      Write the JSON as bytes, then close the stream.
      Parameters:
      instance - instance to write
      dataOutputStream - an output stream that will always be closed
      Throws:
      IOException - on any failure

    • toBytes

      public byte[] toBytes(T instance) throws IOException
      Convert JSON to bytes.
      Parameters:
      instance - instance to convert
      Returns:
      a byte array
      Throws:
      IOException - IO problems

    • fromBytes

      public T fromBytes(byte[] bytes) throws IOException
      Deserialize from a byte array.
      Parameters:
      bytes - byte array
      Returns:
      byte array.
      Throws:
      IOException - IO problems
      EOFException - not enough data

    • toJson

      public String toJson(T instance) throws com.fasterxml.jackson.core.JsonProcessingException
      Convert an instance to a JSON string.
      Parameters:
      instance - instance to convert
      Returns:
      a JSON string description
      Throws:
      com.fasterxml.jackson.core.JsonProcessingException - Json generation problems

    • toString

      public String toString(T instance)
      Convert an instance to a string form for output. This is a robust operation which will convert any JSON-generating exceptions into error text.
      Parameters:
      instance - non-null instance
      Returns:
      a JSON string