/*
* @(#)Statement.java 1.31 06/05/23
*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.beans;
import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Array;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import com.sun.beans.ObjectHandler;
import sun.reflect.misc.MethodUtil;
/**
* A <code>Statement</code> object represents a primitive statement
* in which a single method is applied to a target and
* a set of arguments - as in <code>"a.setFoo(b)"</code>.
* Note that where this example uses names
* to denote the target and its argument, a statement
* object does not require a name space and is constructed with
* the values themselves.
* The statement object associates the named method
* with its environment as a simple set of values:
* the target and an array of argument values.
*
* @since 1.4
*
* @version 1.31 05/23/06
* @author Philip Milne
*/
public class Statement {
private static Object[] emptyArray = new Object[]{};
static ExceptionListener defaultExceptionListener = new ExceptionListener() {
public void exceptionThrown(Exception e) {
System.err.println(e);
// e.printStackTrace();
System.err.println("Continuing ...");
}
};
Object target;
String methodName;
Object[] arguments;
/**
* Creates a new <code>Statement</code> object with a <code>target</code>,
* <code>methodName</code> and <code>arguments</code> as per the parameters.
*
* @param target The target of this statement.
* @param methodName The methodName of this statement.
* @param arguments The arguments of this statement. If <code>null</code> then an empty array will be used.
*
*/
public Statement(Object target, String methodName, Object[] arguments) {
this.target = target;
this.methodName = methodName;
this.arguments = (arguments == null) ? emptyArray : arguments;
}
/**
* Returns the target of this statement.
*
* @return The target of this statement.
*/
public Object getTarget() {
return target;
}
/**
* Returns the name of the method.
*
* @return The name of the method.
*/
public String getMethodName() {
return methodName;
}
/**
* Returns the arguments of this statement.
*
* @return the arguments of this statement.
*/
public Object[] getArguments() {
return arguments;
}
/**
* The execute method finds a method whose name is the same
* as the methodName property, and invokes the method on
* the target.
*
* When the target's class defines many methods with the given name
* the implementation should choose the most specific method using
* the algorithm specified in the Java Language Specification
* (15.11). The dynamic class of the target and arguments are used
* in place of the compile-time type information and, like the
* <code>java.lang.reflect.Method</code> class itself, conversion between
* primitive values and their associated wrapper classes is handled
* internally.
* <p>
* The following method types are handled as special cases:
* <ul>
* <li>
* Static methods may be called by using a class object as the target.
* <li>
* The reserved method name "new" may be used to call a class's constructor
* as if all classes defined static "new" methods. Constructor invocations
* are typically considered <code>Expression</code>s rather than <code>Statement</code>s
* as they return a value.
* <li>
* The method names "get" and "set" defined in the <code>java.util.List</code>
* interface may also be applied to array instances, mapping to
* the static methods of the same name in the <code>Array</code> class.
* </ul>
*/
public void execute() throws Exception {
invoke();
}
Object invoke() throws Exception {
Object target = getTarget();
String methodName = getMethodName();
if (target == null || methodName == null) {
throw new NullPointerException((target == null ? "target" :
"methodName") + " should not be null");
}
Object[] arguments = getArguments();
// Class.forName() won't load classes outside
// of core from a class inside core. Special
// case this method.
if (target == Class.class && methodName.equals("forName")) {
return ObjectHandler.classForName((String)arguments[0]);
}
Class[] argClasses = new Class[arguments.length];
for(int i = 0; i < arguments.length; i++) {
argClasses[i] = (arguments[i] == null) ? null : arguments[i].getClass();
}
AccessibleObject m = null;
if (target instanceof Class) {
/*
For class methods, simluate the effect of a meta class
by taking the union of the static methods of the
actual class, with the instance methods of "Class.class"
and the overloaded "newInstance" methods defined by the
constructors.
This way "System.class", for example, will perform both
the static method getProperties() and the instance method
getSuperclass() defined in "Class.class".
*/
if (methodName.equals("new")) {
methodName = "newInstance";
}
// Provide a short form for array instantiation by faking an nary-constructor.
if (methodName.equals("newInstance") && ((Class)target).isArray()) {
Object result = Array.newInstance(((Class)target).getComponentType(), arguments.length);
for(int i = 0; i < arguments.length; i++) {
Array.set(result, i, arguments[i]);
}
return result;
}
if (methodName.equals("newInstance") && arguments.length != 0) {
// The Character class, as of 1.4, does not have a constructor
// which takes a String. All of the other "wrapper" classes
// for Java's primitive types have a String constructor so we
// fake such a constructor here so that this special case can be
// ignored elsewhere.
if (target == Character.class && arguments.length == 1 &&
argClasses[0] == String.class) {
return new Character(((String)arguments[0]).charAt(0));
}
m = ReflectionUtils.getConstructor((Class)target, argClasses);
}
if (m == null && target != Class.class) {
m = ReflectionUtils.getMethod((Class)target, methodName, argClasses);
}
if (m == null) {
m = ReflectionUtils.getMethod(Class.class, methodName, argClasses);
}
}
else {
/*
This special casing of arrays is not necessary, but makes files
involving arrays much shorter and simplifies the archiving infrastrcure.
The Array.set() method introduces an unusual idea - that of a static method
changing the state of an instance. Normally statements with side
effects on objects are instance methods of the objects themselves
and we reinstate this rule (perhaps temporarily) by special-casing arrays.
*/
if (target.getClass().isArray() &&
(methodName.equals("set") || methodName.equals("get"))) {
int index = ((Integer)arguments[0]).intValue();
if (methodName.equals("get")) {
return Array.get(target, index);
}
else {
Array.set(target, index, arguments[1]);
return null;
}
}
m = ReflectionUtils.getMethod(target.getClass(), methodName, argClasses);
}
if (m != null) {
try {
if (m instanceof Method) {
return MethodUtil.invoke((Method)m, target, arguments);
}
else {
return ((Constructor)m).newInstance(arguments);
}
}
catch (IllegalAccessException iae) {
throw new Exception("Statement cannot invoke: " +
methodName + " on " + target.getClass(),
iae);
}
catch (InvocationTargetException ite) {
Throwable te = ite.getTargetException();
if (te instanceof Exception) {
throw (Exception)te;
}
else {
throw ite;
}
}
}
throw new NoSuchMethodException(toString());
}
String instanceName(Object instance) {
if (instance == null) {
return "null";
} else if (instance.getClass() == String.class) {
return "\""+(String)instance + "\"";
} else {
// Note: there is a minor problem with using the non-caching
// NameGenerator method. The return value will not have
// specific information about the inner class name. For example,
// In 1.4.2 an inner class would be represented as JList$1 now
// would be named Class.
return NameGenerator.unqualifiedClassName(instance.getClass());
}
}
/**
* Prints the value of this statement using a Java-style syntax.
*/
public String toString() {
// Respect a subclass's implementation here.
Object target = getTarget();
String methodName = getMethodName();
Object[] arguments = getArguments();
StringBuffer result = new StringBuffer(instanceName(target) + "." + methodName + "(");
int n = arguments.length;
for(int i = 0; i < n; i++) {
result.append(instanceName(arguments[i]));
if (i != n -1) {
result.append(", ");
}
}
result.append(");");
return result.toString();
}
}
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