methodutils.java

来自「这是一个有关common beanutils 的源码」· Java 代码 · 共 1,358 行 · 第 1/4 页

        }
        if ( bestMatch != null ){
                 cacheMethod(md, bestMatch);
        } else {
        // didn't find a match
               log.trace("No match found.");
        }
        
        return bestMatch;                                        
    }

    /**
     * Try to make the method accessible
     * @param method The source arguments
     */
    private static void setMethodAccessible(Method method) {
        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
            Log log = LogFactory.getLog(MethodUtils.class);
            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);
        }
    }

    /**
     * Returns the sum of the object transformation cost for each class in the source
     * argument list.
     * @param srcArgs The source arguments
     * @param destArgs The destination arguments
     * @return The total transformation cost
     */
    private static float getTotalTransformationCost(Class[] srcArgs, Class[] destArgs) {

        float totalCost = 0.0f;
        for (int i = 0; i < srcArgs.length; i++) {
            Class srcClass, destClass;
            srcClass = srcArgs[i];
            destClass = destArgs[i];
            totalCost += getObjectTransformationCost(srcClass, destClass);
        }

        return totalCost;
    }
    
    /**
     * Gets the number of steps required needed to turn the source class into the 
     * destination class. This represents the number of steps in the object hierarchy 
     * graph.
     * @param srcClass The source class
     * @param destClass The destination class
     * @return The cost of transforming an object
     */
    private static float getObjectTransformationCost(Class srcClass, Class destClass) {
        float cost = 0.0f;
        while (destClass != null && !destClass.equals(srcClass)) {
            if (destClass.isInterface() && isAssignmentCompatible(destClass,srcClass)) {
                // slight penalty for interface match. 
                // we still want an exact match to override an interface match, but  
                // an interface match should override anything where we have to get a 
                // superclass.
                cost += 0.25f;
                break;
            }
            cost++;
            destClass = destClass.getSuperclass();
        }

        /*
         * If the destination class is null, we've travelled all the way up to 
         * an Object match. We'll penalize this by adding 1.5 to the cost.
         */
        if (destClass == null) {
            cost += 1.5f;
        }

        return cost;
    }
    
    
    /**
     * <p>Determine whether a type can be used as a parameter in a method invocation.
     * This method handles primitive conversions correctly.</p>
     *
     * <p>In order words, it will match a <code>Boolean</code> to a <code>boolean</code>,
     * a <code>Long</code> to a <code>long</code>,
     * a <code>Float</code> to a <code>float</code>,
     * a <code>Integer</code> to a <code>int</code>,
     * and a <code>Double</code> to a <code>double</code>.
     * Now logic widening matches are allowed.
     * For example, a <code>Long</code> will not match a <code>int</code>.
     *
     * @param parameterType the type of parameter accepted by the method
     * @param parameterization the type of parameter being tested 
     *
     * @return true if the assignement is compatible.
     */
    public static final boolean isAssignmentCompatible(Class parameterType, Class parameterization) {
        // try plain assignment
        if (parameterType.isAssignableFrom(parameterization)) {
            return true;
        }
        
        if (parameterType.isPrimitive()) {
            // this method does *not* do widening - you must specify exactly
            // is this the right behaviour?
            Class parameterWrapperClazz = getPrimitiveWrapper(parameterType);
            if (parameterWrapperClazz != null) {
                return parameterWrapperClazz.equals(parameterization);
            }
        }
        
        return false;
    }
    
    /**
     * Gets the wrapper object class for the given primitive type class.
     * For example, passing <code>boolean.class</code> returns <code>Boolean.class</code>
     * @param primitiveType the primitive type class for which a match is to be found
     * @return the wrapper type associated with the given primitive 
     * or null if no match is found
     */
    public static Class getPrimitiveWrapper(Class primitiveType) {
        // does anyone know a better strategy than comparing names?
        if (boolean.class.equals(primitiveType)) {
            return Boolean.class;
        } else if (float.class.equals(primitiveType)) {
            return Float.class;
        } else if (long.class.equals(primitiveType)) {
            return Long.class;
        } else if (int.class.equals(primitiveType)) {
            return Integer.class;
        } else if (short.class.equals(primitiveType)) {
            return Short.class;
        } else if (byte.class.equals(primitiveType)) {
            return Byte.class;
        } else if (double.class.equals(primitiveType)) {
            return Double.class;
        } else if (char.class.equals(primitiveType)) {
            return Character.class;
        } else {
            
            return null;
        }
    }

    /**
     * Gets the class for the primitive type corresponding to the primitive wrapper class given.
     * For example, an instance of <code>Boolean.class</code> returns a <code>boolean.class</code>. 
     * @param wrapperType the 
     * @return the primitive type class corresponding to the given wrapper class,
     * null if no match is found
     */
    public static Class getPrimitiveType(Class wrapperType) {
        // does anyone know a better strategy than comparing names?
        if (Boolean.class.equals(wrapperType)) {
            return boolean.class;
        } else if (Float.class.equals(wrapperType)) {
            return float.class;
        } else if (Long.class.equals(wrapperType)) {
            return long.class;
        } else if (Integer.class.equals(wrapperType)) {
            return int.class;
        } else if (Short.class.equals(wrapperType)) {
            return short.class;
        } else if (Byte.class.equals(wrapperType)) {
            return byte.class;
        } else if (Double.class.equals(wrapperType)) {
            return double.class;
        } else if (Character.class.equals(wrapperType)) {
            return char.class;
        } else {
            Log log = LogFactory.getLog(MethodUtils.class);
            if (log.isDebugEnabled()) {
                log.debug("Not a known primitive wrapper class: " + wrapperType);
            }
            return null;
        }
    }
    
    /**
     * Find a non primitive representation for given primitive class.
     *
     * @param clazz the class to find a representation for, not null
     * @return the original class if it not a primitive. Otherwise the wrapper class. Not null
     */
    public static Class toNonPrimitiveClass(Class clazz) {
        if (clazz.isPrimitive()) {
            Class primitiveClazz = MethodUtils.getPrimitiveWrapper(clazz);
            // the above method returns 
            if (primitiveClazz != null) {
                return primitiveClazz;
            } else {
                return clazz;
            }
        } else {
            return clazz;
        }
    }
    

    /**
     * Return the method from the cache, if present.
     *
     * @param md The method descriptor
     * @return The cached method
     */
    private static Method getCachedMethod(MethodDescriptor md) {
        if (CACHE_METHODS) {
            Reference methodRef = (Reference)cache.get(md);
            if (methodRef != null) {
                return (Method)methodRef.get();
            }
        }
        return null;
    }

    /**
     * Add a method to the cache.
     *
     * @param md The method descriptor
     * @param method The method to cache
     */
    private static void cacheMethod(MethodDescriptor md, Method method) {
        if (CACHE_METHODS) {
            if (method != null) {
                cache.put(md, new WeakReference(method));
            }
        }
    }

    /**
     * Represents the key to looking up a Method by reflection.
     */
    private static class MethodDescriptor {
        private Class cls;
        private String methodName;
        private Class[] paramTypes;
        private boolean exact;
        private int hashCode;

        /**
         * The sole constructor.
         *
         * @param cls  the class to reflect, must not be null
         * @param methodName  the method name to obtain
         * @param paramTypes the array of classes representing the paramater types
         * @param exact whether the match has to be exact.
         */
        public MethodDescriptor(Class cls, String methodName, Class[] paramTypes, boolean exact) {
            if (cls == null) {
                throw new IllegalArgumentException("Class cannot be null");
            }
            if (methodName == null) {
                throw new IllegalArgumentException("Method Name cannot be null");
            }
            if (paramTypes == null) {
                paramTypes = EMPTY_CLASS_PARAMETERS;
            }

            this.cls = cls;
            this.methodName = methodName;
            this.paramTypes = paramTypes;
            this.exact= exact;

            this.hashCode = methodName.length();
        }
        /**
         * Checks for equality.
         * @param obj object to be tested for equality
         * @return true, if the object describes the same Method.
         */
        public boolean equals(Object obj) {
            if (!(obj instanceof MethodDescriptor)) {
                return false;
            }
            MethodDescriptor md = (MethodDescriptor)obj;

            return (
                exact == md.exact &&
                methodName.equals(md.methodName) &&
                cls.equals(md.cls) &&
                java.util.Arrays.equals(paramTypes, md.paramTypes)
            );
        }
        /**
         * Returns the string length of method name. I.e. if the
         * hashcodes are different, the objects are different. If the
         * hashcodes are the same, need to use the equals method to
         * determine equality.
         * @return the string length of method name.
         */
        public int hashCode() {
            return hashCode;
        }
    }
}