CompositeDataView (Java SE 15 & JDK 15) (original) (raw)

All Known Implementing Classes:

[GarbageCollectionNotificationInfo](../../../../jdk.management/com/sun/management/GarbageCollectionNotificationInfo.html "class in com.sun.management"), [GcInfo](../../../../jdk.management/com/sun/management/GcInfo.html "class in com.sun.management")

public interface CompositeDataView

A Java class can implement this interface to indicate how it is to be converted into a CompositeData by the MXBean framework.

A typical way to use this class is to add extra items to theCompositeData in addition to the ones that are declared in theCompositeType supplied by the MXBean framework. To do this, you must create another CompositeType that has all the same items, plus your extra items.

For example, suppose you have a class Measure that consists of a String called units and a value that is either along or a double. It might look like this:

public class Measure implements CompositeDataView { private String units; private Number value; // a Long or a Double

 public Measure(String units, Number value) {
     this.units = units;
     this.value = value;
 }

 public static Measure from(CompositeData cd) {
     return new Measure((String) cd.get("units"),
                        (Number) cd.get("value"));
 }

 public String getUnits() {
     return units;
 }

 // Can't be called getValue(), because Number is not a valid type
 // in an MXBean, so the implied "value" property would be rejected.
 public Number _getValue() {
     return value;
 }

 public CompositeData toCompositeData(CompositeType ct) {
     try {
         `List<String> itemNames = new ArrayList<String>(ct.keySet());`
         `List<String> itemDescriptions = new ArrayList<String>();`
         `List<OpenType<?>> itemTypes = new ArrayList<OpenType<?>>();`
         for (String item : itemNames) {
             itemDescriptions.add(ct.getDescription(item));
             itemTypes.add(ct.getType(item));
         }
         itemNames.add("value");
         itemDescriptions.add("long or double value of the measure");
         itemTypes.add((value instanceof Long) ? SimpleType.LONG :
                       SimpleType.DOUBLE);
         CompositeType xct =
             new CompositeType(ct.getTypeName(),
                               ct.getDescription(),
                               itemNames.toArray(new String[0]),
                               itemDescriptions.toArray(new String[0]),
                               itemTypes.toArray(new OpenType<?>[0]));
         CompositeData cd =
             new CompositeDataSupport(xct,
                                      new String[] {"units", "value"},
                                      new Object[] {units, value});
         assert ct.isValue(cd);  // check we've done it right
         return cd;
     } catch (Exception e) {
         throw new RuntimeException(e);
     }
 }

}

The CompositeType that will appear in the openType field of the Descriptor for an attribute or operation of this type will show only the units item, but the actualCompositeData that is generated will have both units andvalue.

Since:

1.6

See Also:

MXBean