methodutils.java

APACHE 公司出的java bean 工具包

    }


    /**
     * <p>Return an accessible method (that is, one that can be invoked via
     * reflection) with given name and a single parameter.  If no such method
     * can be found, return <code>null</code>.
     * Basically, a convenience wrapper that constructs a <code>Class</code>
     * array for you.</p>
     *
     * @param clazz get method from this class
     * @param methodName get method with this name
     * @param parameterType taking this type of parameter
     * @return The accessible method
     */
    public static Method getAccessibleMethod(
            Class clazz,
            String methodName,
            Class parameterType) {

        Class[] parameterTypes = {parameterType};
        return getAccessibleMethod(clazz, methodName, parameterTypes);

    }


    /**
     * <p>Return an accessible method (that is, one that can be invoked via
     * reflection) with given name and parameters.  If no such method
     * can be found, return <code>null</code>.
     * This is just a convenient wrapper for
     * {@link #getAccessibleMethod(Method method)}.</p>
     *
     * @param clazz get method from this class
     * @param methodName get method with this name
     * @param parameterTypes with these parameters types
     * @return The accessible method
     */
    public static Method getAccessibleMethod(
            Class clazz,
            String methodName,
            Class[] parameterTypes) {

        try {
            MethodDescriptor md = new MethodDescriptor(clazz, methodName, parameterTypes, true);
            // Check the cache first
            Method method = (Method)cache.get(md);
            if (method != null) {
                return method;
            }
            
            method =  getAccessibleMethod
                    (clazz.getMethod(methodName, parameterTypes));
            cache.put(md, method);
            return method;
        } catch (NoSuchMethodException e) {
            return (null);
        }

    }


    /**
     * <p>Return an accessible method (that is, one that can be invoked via
     * reflection) that implements the specified Method.  If no such method
     * can be found, return <code>null</code>.</p>
     *
     * @param method The method that we wish to call
     * @return The accessible method
     */
    public static Method getAccessibleMethod(Method method) {

        // Make sure we have a method to check
        if (method == null) {
            return (null);
        }

        // If the requested method is not public we cannot call it
        if (!Modifier.isPublic(method.getModifiers())) {
            return (null);
        }

        // If the declaring class is public, we are done
        Class clazz = method.getDeclaringClass();
        if (Modifier.isPublic(clazz.getModifiers())) {
            return (method);
        }

        String methodName      = method.getName();
        Class[] parameterTypes = method.getParameterTypes();

        // Check the implemented interfaces and subinterfaces
        method =
                getAccessibleMethodFromInterfaceNest(clazz,
                        methodName,
                        parameterTypes);

        // Check the superclass chain
        if (method == null) {
            method = getAccessibleMethodFromSuperclass(clazz,
                        methodName,
                        parameterTypes);
        }

        return (method);

    }


    // -------------------------------------------------------- Private Methods

    /**
     * <p>Return an accessible method (that is, one that can be invoked via
     * reflection) by scanning through the superclasses. If no such method
     * can be found, return <code>null</code>.</p>
     *
     * @param clazz Class to be checked
     * @param methodName Method name of the method we wish to call
     * @param parameterTypes The parameter type signatures
     */
    private static Method getAccessibleMethodFromSuperclass
            (Class clazz, String methodName, Class[] parameterTypes) {

        Class parentClazz = clazz.getSuperclass();
        while (parentClazz != null) {
            if (Modifier.isPublic(parentClazz.getModifiers())) {
                try {
                    return parentClazz.getMethod(methodName, parameterTypes);
                } catch (NoSuchMethodException e) {
                    return null;
                }
            }
            parentClazz = parentClazz.getSuperclass();
        }
        return null;
    }

    /**
     * <p>Return an accessible method (that is, one that can be invoked via
     * reflection) that implements the specified method, by scanning through
     * all implemented interfaces and subinterfaces.  If no such method
     * can be found, return <code>null</code>.</p>
     *
     * <p> There isn't any good reason why this method must be private.
     * It is because there doesn't seem any reason why other classes should
     * call this rather than the higher level methods.</p>
     *
     * @param clazz Parent class for the interfaces to be checked
     * @param methodName Method name of the method we wish to call
     * @param parameterTypes The parameter type signatures
     */
    private static Method getAccessibleMethodFromInterfaceNest
            (Class clazz, String methodName, Class[] parameterTypes) {

        Method method = null;

        // Search up the superclass chain
        for (; clazz != null; clazz = clazz.getSuperclass()) {

            // Check the implemented interfaces of the parent class
            Class[] interfaces = clazz.getInterfaces();
            for (int i = 0; i < interfaces.length; i++) {

                // Is this interface public?
                if (!Modifier.isPublic(interfaces[i].getModifiers())) {
                    continue;
                }

                // Does the method exist on this interface?
                try {
                    method = interfaces[i].getDeclaredMethod(methodName,
                            parameterTypes);
                } catch (NoSuchMethodException e) {
                    /* Swallow, if no method is found after the loop then this
                     * method returns null.
                     */
                }
                if (method != null) {
                    break;
                }

                // Recursively check our parent interfaces
                method =
                        getAccessibleMethodFromInterfaceNest(interfaces[i],
                                methodName,
                                parameterTypes);
                if (method != null) {
                    break;
                }

            }

        }

        // If we found a method return it
        if (method != null) {
            return (method);
        }

        // We did not find anything
        return (null);

    }

    /**
     * <p>Find an accessible method that matches the given name and has compatible parameters.
     * Compatible parameters mean that every method parameter is assignable from 
     * the given parameters.
     * In other words, it finds a method with the given name 
     * that will take the parameters given.<p>
     *
     * <p>This method is slightly undeterminstic since it loops 
     * through methods names and return the first matching method.</p>
     * 
     * <p>This method is used by 
     * {@link 
     * #invokeMethod(Object object,String methodName,Object [] args,Class[] parameterTypes)}.
     *
     * <p>This method can match primitive parameter by passing in wrapper classes.
     * For example, a <code>Boolean</code> will match a primitive <code>boolean</code>
     * parameter.
     *
     * @param clazz find method in this class
     * @param methodName find method with this name
     * @param parameterTypes find method with compatible parameters 
     * @return The accessible method
     */
    public static Method getMatchingAccessibleMethod(
                                                Class clazz,
                                                String methodName,
                                                Class[] parameterTypes) {
        // trace logging
        Log log = LogFactory.getLog(MethodUtils.class);
        if (log.isTraceEnabled()) {
            log.trace("Matching name=" + methodName + " on " + clazz);
        }
        MethodDescriptor md = new MethodDescriptor(clazz, methodName, parameterTypes, false);
        
        // see if we can find the method directly
        // most of the time this works and it's much faster
        try {
            // Check the cache first
            Method method = (Method)cache.get(md);
            if (method != null) {
                return method;
            }

            method = clazz.getMethod(methodName, parameterTypes);
            if (log.isTraceEnabled()) {
                log.trace("Found straight match: " + method);
                log.trace("isPublic:" + Modifier.isPublic(method.getModifiers()));
            }
            
            try {
                //
                // XXX Default access superclass workaround
                //
                // When a public class has a default access superclass
                // with public methods, these methods are accessible.
                // Calling them from compiled code works fine.
                //
                // Unfortunately, using reflection to invoke these methods
                // seems to (wrongly) to prevent access even when the method
                // modifer is public.
                //
                // The following workaround solves the problem but will only
                // work from sufficiently privilages code. 
                //
                // Better workarounds would be greatfully accepted.
                //
                method.setAccessible(true);
                
            } catch (SecurityException se) {
                // log but continue just in case the method.invoke works anyway
                if (!loggedAccessibleWarning) {
                    boolean vulnerableJVM = false;
                    try {
                        String specVersion = System.getProperty("java.specification.version");
                        if (specVersion.charAt(0) == '1' && 
                                (specVersion.charAt(2) == '0' ||
                                 specVersion.charAt(2) == '1' ||
                                 specVersion.charAt(2) == '2' ||
                                 specVersion.charAt(2) == '3')) {
                                 
                            vulnerableJVM = true;
                        }
                    } catch (SecurityException e) {
                        // don't know - so display warning
                        vulnerableJVM = true;
                    }
                    if (vulnerableJVM) {
                        log.warn(
                            "Current Security Manager restricts use of workarounds for reflection bugs "
                            + " in pre-1.4 JVMs.");
                    }
                    loggedAccessibleWarning = true;
                }
                log.debug(
                        "Cannot setAccessible on method. Therefore cannot use jvm access bug workaround.", 
                        se);
            }
            cache.put(md, method);
            return method;
            
        } catch (NoSuchMethodException e) { /* SWALLOW */ }
        
        // search through all methods 
        int paramSize = parameterTypes.length;
        Method bestMatch = null;
        Method[] methods = clazz.getMethods();
        float bestMatchCost = Float.MAX_VALUE;
        float myCost = Float.MAX_VALUE;
        for (int i = 0, size = methods.length; i < size ; i++) {
            if (methods[i].getName().equals(methodName)) {
                // log some trace information