Class Attribute

  • All Implemented Interfaces:
    java.io.Serializable, Metadata

    public class Attribute
    extends java.lang.Object
    implements Metadata
    An attribute is a (name, value) pair of metadata attached to a primary data object such as dataset, group or named datatype.

    Like a dataset, an attribute has a name, datatype and dataspace.

    For more details on attibutes, see {@link HDF5 User's Guide}

    The following code is an example of an attribute with 1D integer array of two elements.

     // Example of creating a new attribute
     // The name of the new attribute
     String name = "Data range";
     // Creating an unsigned 1-byte integer datatype
     Datatype type = new Datatype(Datatype.CLASS_INTEGER, // class
                                  1,                      // size in bytes
                                  Datatype.ORDER_LE,      // byte order
                                  Datatype.SIGN_NONE);    // signed or unsigned
     // 1-D array of size two
     long[] dims = {2};
     // The value of the attribute
     int[] value = {0, 255};
     // Create a new attribute
     Attribute dataRange = new Attribute(name, type, dims);
     // Set the attribute value
     dataRange.setValue(value);
     // See FileFormat.writeAttribute() for how to attach an attribute to an object,
    Version:
    1.1 9/4/2007
    Author:
    Peter X. Cao
    See Also:
    FileFormat.writeAttribute(HObject, Attribute, boolean), Datatype, Serialized Form
    • Field Summary

      Fields 
      Modifier and Type Field Description
      protected boolean isScalar
      flag to indicate if the dataset is a single scalar point
    • Constructor Summary

      Constructors 
      Constructor Description
      Attribute​(java.lang.String attrName, Datatype attrType, long[] attrDims)
      Create an attribute with specified name, data type and dimension sizes.
      Attribute​(java.lang.String attrName, Datatype attrType, long[] attrDims, java.lang.Object attrValue)
      Create an attribute with specific name and value.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      long[] getDataDims()
      Returns the dimension sizes of the data value of the attribute.
      java.lang.String getName()
      Returns the name of the attribute.
      java.lang.Object getProperty​(java.lang.String key)
      get a property for a given key.
      java.util.Collection<java.lang.String> getPropertyKeys()
      get all property keys.
      int getRank()
      Returns the rank (number of dimensions) of the attribute.
      Datatype getType()
      Returns the datatype of the attribute.
      java.lang.Object getValue()
      Returns the value of the attribute.
      boolean isScalar()  
      boolean isUnsigned()
      Checks if the data type of this attribute is an unsigned integer.
      void setProperty​(java.lang.String key, java.lang.Object value)
      set a property for the attribute.
      void setValue​(java.lang.Object theValue)
      Sets the value of the attribute.
      java.lang.String toString()
      Return the name of the attribute.
      java.lang.String toString​(java.lang.String delimiter)
      Returns a string representation of the data value of the attribute.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
    • Field Detail

      • isScalar

        protected boolean isScalar
        flag to indicate if the dataset is a single scalar point
    • Constructor Detail

      • Attribute

        public Attribute​(java.lang.String attrName,
                         Datatype attrType,
                         long[] attrDims)
        Create an attribute with specified name, data type and dimension sizes. For scalar attribute, the dimension size can be either an array of size one or null, and the rank can be either 1 or zero. Attribute is a general class and is independent of file format, e.g., the implementation of attribute applies to both HDF4 and HDF5.

        The following example creates a string attribute with the name "CLASS" and value "IMAGE".

         long[] attrDims = { 1 };
         String attrName = "CLASS";
         String[] classValue = { "IMAGE" };
         Datatype attrType = new H5Datatype(Datatype.CLASS_STRING, classValue[0].length() + 1, -1, -1);
         Attribute attr = new Attribute(attrName, attrType, attrDims);
         attr.setValue(classValue);
         
        Parameters:
        attrName - the name of the attribute.
        attrType - the datatype of the attribute.
        attrDims - the dimension sizes of the attribute, null for scalar attribute
        See Also:
        Datatype
      • Attribute

        public Attribute​(java.lang.String attrName,
                         Datatype attrType,
                         long[] attrDims,
                         java.lang.Object attrValue)
        Create an attribute with specific name and value. For scalar attribute, the dimension size can be either an array of size one or null, and the rank can be either 1 or zero. Attribute is a general class and is independent of file format, e.g., the implementation of attribute applies to both HDF4 and HDF5.

        The following example creates a string attribute with the name "CLASS" and value "IMAGE".

         long[] attrDims = { 1 };
                                  String attrName = "CLASS";
                                                             String[] classValue = { "IMAGE" };
                                                                                                Datatype attrType = new H5Datatype(
                                                                                                                          Datatype.CLASS_STRING,
                                                                                                                          classValue[0]
                                                                                                                                  .length() + 1,
                                                                                                                          -1, -1);
                                                                                                                                   Attribute attr = new Attribute(
                                                                                                                                                          attrName,
                                                                                                                                                          attrType,
                                                                                                                                                          attrDims,
                                                                                                                                                          classValue);
         
        Parameters:
        attrName - the name of the attribute.
        attrType - the datatype of the attribute.
        attrDims - the dimension sizes of the attribute, null for scalar attribute
        attrValue - the value of the attribute, null if no value
        See Also:
        Datatype
    • Method Detail

      • getValue

        public java.lang.Object getValue()
        Returns the value of the attribute. For atomic datatype, this will be an 1D array of integers, floats and strings. For compound datatype, it will be an 1D array of strings with field members separated by comma. For example, "{0, 10.5}, {255, 20.0}, {512, 30.0}" is a cmpound attribute of {int, float} of three data points.
        Specified by:
        getValue in interface Metadata
        Returns:
        the value of the attribute, or null if failed to retrieve data from file.
      • setProperty

        public void setProperty​(java.lang.String key,
                                java.lang.Object value)
        set a property for the attribute.
      • getProperty

        public java.lang.Object getProperty​(java.lang.String key)
        get a property for a given key.
      • getPropertyKeys

        public java.util.Collection<java.lang.String> getPropertyKeys()
        get all property keys.
      • setValue

        public void setValue​(java.lang.Object theValue)
        Sets the value of the attribute. It returns null if failed to retrieve the name from file.
        Specified by:
        setValue in interface Metadata
        Parameters:
        theValue - The value of the attribute to set
      • getName

        public java.lang.String getName()
        Returns the name of the attribute.
        Returns:
        the name of the attribute.
      • getRank

        public int getRank()
        Returns the rank (number of dimensions) of the attribute. It returns a negative number if failed to retrieve the dimension information from file.
        Returns:
        the number of dimensions of the attribute.
      • getDataDims

        public long[] getDataDims()
        Returns the dimension sizes of the data value of the attribute. It returns null if failed to retrieve the dimension information from file.
        Returns:
        the dimension sizes of the attribute.
      • getType

        public Datatype getType()
        Returns the datatype of the attribute. It returns null if failed to retrieve the datatype information from file.
        Returns:
        the datatype of the attribute.
      • isScalar

        public boolean isScalar()
        Returns:
        true if the data is a single scalar point; otherwise, returns false.
      • isUnsigned

        public boolean isUnsigned()
        Checks if the data type of this attribute is an unsigned integer.
        Returns:
        true if the data type of the attribute is an unsigned integer; otherwise returns false.
      • toString

        public java.lang.String toString()
        Return the name of the attribute.
        Overrides:
        toString in class java.lang.Object
        See Also:
        toString(String delimiter)
      • toString

        public java.lang.String toString​(java.lang.String delimiter)
        Returns a string representation of the data value of the attribute. For example, "0, 255".

        For compound datatype, it will be an 1D array of strings with field members separated by comma. For example, "{0, 10.5}, {255, 20.0}, {512, 30.0}" is a compound attribute of {int, float} of three data points.

        Parameters:
        delimiter - The delimiter to separate individual data point. It can be comma, semicolon, tab or space. For example, to String(",") will separate data by comma.
        Returns:
        the string representation of the data values.