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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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package javax.management.openmbean;
import com.sun.jmx.mbeanserver.MXBeanLookup;
import com.sun.jmx.mbeanserver.OpenConverter;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
An InvocationHandler that forwards getter methods to a CompositeData. If you have an interface that contains only getter methods (such as String getName() or boolean isActive()) then you can use this class in conjunction with the Proxy class to produce an implementation of the interface where each getter returns the value of the corresponding item in a CompositeData.
For example, suppose you have an interface like this:
public interface NamedNumber {
public int getNumber();
public String getName();
}
and a CompositeData constructed like this:
CompositeData cd = new CompositeDataSupport( someCompositeType, new String[] {"number", "name"}, new Object[] {5, "five"}
);
then you can construct an object implementing NamedNumber and backed by the object cd like this:
InvocationHandler handler =
new CompositeDataInvocationHandler(cd);
NamedNumber nn = (NamedNumber)
Proxy.newProxyInstance(NamedNumber.class.getClassLoader(),
new Class[] {NamedNumber.class},
handler);
A call to 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 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 getNumber(), the handler will first look for an item called Number, then for number. If the getter is called getnumber(), then the item must be called number.
If the method given to invoke is the method boolean equals(Object) inherited from Object, then it will return true if and only if the argument is a Proxy whose InvocationHandler is also a
CompositeDataInvocationHandler and whose backing
CompositeData is equal (not necessarily identical) to this object's. If the method given to invoke is the method int hashCode() inherited from Object, then it will return a value that is consistent with this definition of
equals: if two objects are equal according to equals, then they will have the same hashCode.
Since: 1.6
/**
<p>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}.</p>
<p>For example, suppose you have an interface like this:
<blockquote>
<pre>
public interface NamedNumber {
public int getNumber();
public String getName();
}
</pre>
</blockquote>
and a {@code CompositeData} constructed like this:
<blockquote>
<pre>
CompositeData cd =
new {@link CompositeDataSupport}(
someCompositeType,
new String[] {"number", "name"},
new Object[] {<b>5</b>, "five"}
);
</pre>
</blockquote>
then you can construct an object implementing {@code NamedNumber}
and backed by the object {@code cd} like this:
<blockquote>
<pre>
InvocationHandler handler =
new CompositeDataInvocationHandler(cd);
NamedNumber nn = (NamedNumber)
Proxy.newProxyInstance(NamedNumber.class.getClassLoader(),
new Class[] {NamedNumber.class},
handler);
</pre>
</blockquote>
A call to {@code nn.getNumber()} will then return <b>5</b>.</p>
<p>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}.</p>
<p>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}.</p>
@since 1.6
*/
public class CompositeDataInvocationHandler implements InvocationHandler {
Construct a handler backed by the given
CompositeData.
Params: - compositeData – the
CompositeData that will supply information to getters.
Throws: - IllegalArgumentException – if
compositeData is null.
/**
<p>Construct a handler backed by the given {@code
CompositeData}.</p>
@param compositeData the {@code CompositeData} that will supply
information to getters.
@throws IllegalArgumentException if {@code compositeData}
is null.
*/
public CompositeDataInvocationHandler(CompositeData compositeData) {
this(compositeData, null);
}
Construct a handler backed by the given
CompositeData.
Params: - mbsc – the
MBeanServerConnection related to this 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. - compositeData – the
CompositeData that will supply information to getters.
Throws: - IllegalArgumentException – if
compositeData is null.
/**
<p>Construct a handler backed by the given {@code
CompositeData}.</p>
@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.
*/
CompositeDataInvocationHandler(CompositeData compositeData,
MXBeanLookup lookup) {
if (compositeData == null)
throw new IllegalArgumentException("compositeData");
this.compositeData = compositeData;
this.lookup = lookup;
}
Return the CompositeData that was supplied to the constructor. Returns: the CompositeData that this handler is backed by. This is never null.
/**
Return the {@code CompositeData} that was supplied to the
constructor.
@return the {@code CompositeData} that this handler is backed
by. This is never null.
*/
public CompositeData getCompositeData() {
assert compositeData != null;
return compositeData;
}
public Object invoke(Object proxy, Method method, Object[] args)
throws Throwable {
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. */
// this plain Method.invoke is called only if the declaring class
// is Object and so it's safe.
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);
}
/* This method is called when equals(Object) is
* called on our proxy and hence forwarded to us. For example, if we
* are a proxy for an interface like this:
* public interface GetString {
* public String string();
* }
* then we must compare equal to another CompositeDataInvocationHandler
* proxy for the same interface and where string() returns the same value.
*
* You might think that we should also compare equal to another
* object that implements GetString directly rather than using
* Proxy, provided that its string() returns the same result as
* ours, and in fact an earlier version of this class did that (by
* converting the other object into a CompositeData and comparing
* that with ours). But in fact that doesn't make a great deal of
* sense because there's absolutely no guarantee that the
* resulting equals would be reflexive (otherObject.equals(this)
* might be false even if this.equals(otherObject) is true), and,
* especially, there's no way we could generate a hashCode() that
* would be equal to otherObject.hashCode() when
* this.equals(otherObject), because we don't know how
* otherObject.hashCode() is computed.
*/
private boolean equals(Object proxy, 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);
}
private final CompositeData compositeData;
private final MXBeanLookup lookup;
}