File Doc Category Size Date Package
CompositeDataInvocationHandler.java API Doc Java SE 6 API 8510 Tue Jun 10 00:26:16 BST 2008 javax.management.openmbean

CompositeDataInvocationHandler

java.lang.Object

public class CompositeDataInvocationHandler extends Object implements InvocationHandler

An {@link InvocationHandler} that forwards getter methods to a {@link CompositeData}. If you have an interface that contains only getter methods (such as {@code String getName()} or {@code boolean isActive()}) then you can use this class in conjunction with the {@link Proxy} class to produce an implementation of the interface where each getter returns the value of the corresponding item in a {@code CompositeData}.

For example, suppose you have an interface like this:

public interface NamedNumber {
public int getNumber();
public String getName();
}

and a {@code CompositeData} constructed like this:

CompositeData cd =
new {@link CompositeDataSupport}(
someCompositeType,
new String[] {"number", "name"},
new Object[] {5, "five"}
);

then you can construct an object implementing {@code NamedNumber} and backed by the object {@code cd} like this:

InvocationHandler handler =
new CompositeDataInvocationHandler(cd);
NamedNumber nn = (NamedNumber)
Proxy.newProxyInstance(NamedNumber.class.getClassLoader(),
new Class[] {NamedNumber.class},
handler);

A call to {@code nn.getNumber()} will then return 5.

If the first letter of the property defined by a getter is a capital, then this handler will look first for an item in the {@code CompositeData} beginning with a capital, then, if that is not found, for an item beginning with the corresponding lowercase letter or code point. For a getter called {@code getNumber()}, the handler will first look for an item called {@code Number}, then for {@code number}. If the getter is called {@code getnumber()}, then the item must be called {@code number}.

If the method given to {@link #invoke invoke} is the method {@code boolean equals(Object)} inherited from {@code Object}, then it will return true if and only if the argument is a {@code Proxy} whose {@code InvocationHandler} is also a {@code CompositeDataInvocationHandler} and whose backing {@code CompositeData} is equal (not necessarily identical) to this object's. If the method given to {@code invoke} is the method {@code int hashCode()} inherited from {@code Object}, then it will return a value that is consistent with this definition of {@code equals}: if two objects are equal according to {@code equals}, then they will have the same {@code hashCode}.

since: 1.6

Fields Summary
private final CompositeData
compositeData
private final MXBeanLookup
lookup
Constructors Summary
public CompositeDataInvocationHandler(CompositeData compositeData)
Construct a handler backed by the given {@code CompositeData}.
param
compositeData the {@code CompositeData} that will supply information to getters.
throws
IllegalArgumentException if {@code compositeData} is null.
this(compositeData, null);
CompositeDataInvocationHandler(CompositeData compositeData, MXBeanLookup lookup)
Construct a handler backed by the given {@code CompositeData}.
param
mbsc the {@code MBeanServerConnection} related to this {@code CompositeData}. This is only relevant if a method in the interface for which this is an invocation handler returns a type that is an MXBean interface. Otherwise, it can be null.
param
compositeData the {@code CompositeData} that will supply information to getters.
throws
IllegalArgumentException if {@code compositeData} is null.
if (compositeData == null) throw new IllegalArgumentException("compositeData"); this.compositeData = compositeData; this.lookup = lookup;
Methods Summary
private boolean equals(java.lang.Object proxy, java.lang.Object other)
if (other == null) return false; final Class proxyClass = proxy.getClass(); final Class otherClass = other.getClass(); if (proxyClass != otherClass) return false; InvocationHandler otherih = Proxy.getInvocationHandler(other); if (!(otherih instanceof CompositeDataInvocationHandler)) return false; CompositeDataInvocationHandler othercdih = (CompositeDataInvocationHandler) otherih; return compositeData.equals(othercdih.compositeData);
public javax.management.openmbean.CompositeData getCompositeData()
Return the {@code CompositeData} that was supplied to the constructor.
return
the {@code CompositeData} that this handler is backed by. This is never null.
assert compositeData != null; return compositeData;
public java.lang.Object invoke(java.lang.Object proxy, java.lang.reflect.Method method, java.lang.Object[] args)
final String methodName = method.getName(); // Handle the methods from java.lang.Object if (method.getDeclaringClass() == Object.class) { if (methodName.equals("toString") && args == null) return "Proxy[" + compositeData + "]"; else if (methodName.equals("hashCode") && args == null) return compositeData.hashCode() + 0x43444948; else if (methodName.equals("equals") && args.length == 1 && method.getParameterTypes()[0] == Object.class) return equals(proxy, args[0]); else { /* Either someone is calling invoke by hand, or it is a non-final method from Object overriden by the generated Proxy. At the time of writing, the only non-final methods in Object that are not handled above are finalize and clone, and these are not overridden in generated proxies. */ return method.invoke(this, args); } } String propertyName = OpenConverter.propertyName(method); if (propertyName == null) { throw new IllegalArgumentException("Method is not getter: " + method.getName()); } Object openValue; if (compositeData.containsKey(propertyName)) openValue = compositeData.get(propertyName); else { String decap = OpenConverter.decapitalize(propertyName); if (compositeData.containsKey(decap)) openValue = compositeData.get(decap); else { final String msg = "No CompositeData item " + propertyName + (decap.equals(propertyName) ? "" : " or " + decap) + " to match " + methodName; throw new IllegalArgumentException(msg); } } OpenConverter converter = OpenConverter.toConverter(method.getGenericReturnType()); return converter.fromOpenValue(lookup, openValue);