CompositeDataView

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

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

For example, suppose you have a class {@code Measure} that consists of a String called {@code units} and a {@code value} that is either a {@code long} or a {@code 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 {
{@code List itemNames = new ArrayList(ct.keySet());}
{@code List itemDescriptions = new ArrayList();}
{@code List> itemTypes = new ArrayList>();}
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 {@code CompositeType} that will appear in the {@code openType} field of the {@link javax.management.Descriptor Descriptor} for an attribute or operation of this type will show only the {@code units} item, but the actual {@code CompositeData} that is generated will have both {@code units} and {@code value}.