是否可以在执行的 JavaScript 代码中拦截 Java 对象的字段(和方法)访问?就像 JSCocoa 中允许处理属性和方法访问的委托一样。
问问题
1478 次
2 回答
5
您可以使用 Context.setWrapFactory 来指定如何包装 Java 对象。这里显示了打印字段访问和方法调用的包装器:
InterceptWrapFactory.java
import org.mozilla.javascript.Context;
import org.mozilla.javascript.Scriptable;
import org.mozilla.javascript.WrapFactory;
public class InterceptWrapFactory extends WrapFactory{
@Override
public Scriptable wrapAsJavaObject(Context cx, Scriptable scope,
Object javaObject, Class<?> staticType) {
return new InterceptNativeObject(scope, javaObject, staticType);
}
}
拦截NativeObject.java
import org.mozilla.javascript.NativeJavaMethod;
import org.mozilla.javascript.NativeJavaObject;
import org.mozilla.javascript.Scriptable;
public class InterceptNativeObject extends NativeJavaObject {
@Override
public Object get(String name, Scriptable start) {
Object res = super.get(name, start);
System.out.println("Field get name="+name+" result="+res);
if (res instanceof NativeJavaMethod) {
NativeJavaMethod method = (NativeJavaMethod) res;
return new JavaMethodWrapper(method);
}
return res;
}
public InterceptNativeObject(Scriptable scope, Object javaObject,
Class<?> staticType) {
super(scope, javaObject, staticType);
}
}
JavaMethodWrapper.java
import org.mozilla.javascript.Context;
import org.mozilla.javascript.Function;
import org.mozilla.javascript.NativeJavaMethod;
import org.mozilla.javascript.Scriptable;
public class JavaMethodWrapper implements Function {
NativeJavaMethod method;
public JavaMethodWrapper(NativeJavaMethod method) {
this.method = method;
}
public boolean hasInstance(Scriptable instance) {
return method.hasInstance(instance);
}
public Object call(Context cx, Scriptable scope, Scriptable thisObj,
Object[] args) {
System.out.println("Call method: "+method);
return method.call(cx, scope, thisObj, args);
}
public boolean has(int index, Scriptable start) {
return method.has(index, start);
}
public Scriptable construct(Context cx, Scriptable scope, Object[] args) {
return method.construct(cx, scope, args);
}
public void put(int index, Scriptable start, Object value) {
method.put(index, start, value);
}
public void delete(int index) {
method.delete(index);
}
public Scriptable createObject(Context cx, Scriptable scope) {
return method.createObject(cx, scope);
}
public boolean has(String name, Scriptable start) {
return method.has(name, start);
}
public void defineConst(String name, Scriptable start) {
method.defineConst(name, start);
}
public void put(String name, Scriptable start, Object value) {
method.put(name, start, value);
}
public void delete(String name) {
method.delete(name);
}
public Scriptable getPrototype() {
return method.getPrototype();
}
public void setPrototype(Scriptable m) {
method.setPrototype(m);
}
public Scriptable getParentScope() {
return method.getParentScope();
}
public void setParentScope(Scriptable m) {
method.setParentScope(m);
}
public Object[] getIds() {
return method.getIds();
}
public Object get(int index, Scriptable start) {
return method.get(index, start);
}
public Object get(String name, Scriptable start) {
return method.get(name, start);
}
public String getClassName() {
return method.getClassName();
}
public Object getDefaultValue(Class<?> typeHint) {
return method.getDefaultValue(typeHint);
}
}
这是一个测试代码:
import java.util.Vector;
import org.mozilla.javascript.Context;
import org.mozilla.javascript.Scriptable;
import org.mozilla.javascript.ScriptableObject;
public class InterceptTest {
public static void main(String[] args) {
Context cx=Context.enter();
cx.setWrapFactory(new InterceptWrapFactory());
Scriptable root=cx.initStandardObjects();
ScriptableObject.putProperty(root,"v", new Vector<String>());
cx.evaluateString(root, "v.add('foo'); v.get(0)", "src", 1, null);
}
}
于 2012-05-11T14:49:27.570 回答
0
作为 hog1e3 建议的替代方案,还可以实现 Scriptable 接口来拦截对类的方法/字段的调用。
于 2012-05-16T07:16:00.197 回答