propertydescriptor.java

gcc的组建

        return constrained;
    }

    /** Set whether the property is constrained.
     ** If the set method throws <CODE>java.beans.PropertyVetoException</CODE>
     ** (or subclass thereof) and the bean implements addVetoableChangeListener()
     ** and removeVetoableChangeListener(), then setConstrained(true) may safely
     ** be called.  Otherwise, the system behavior is undefined.
     ** <B>Spec note:</B> given those strict parameters, it would be nice if it
     ** got set automatically by detection, but oh well.<P>
     ** When a property is constrained, its set method is required to:<P>
     ** <OL>
     ** <LI>Fire the <CODE>VetoableChangeListener.vetoableChange()</CODE>
     **     event notifying others of the change and allowing them a chance to
     **     say it is a bad thing.</LI>
     ** <LI>If any of the listeners throws a PropertyVetoException, then
     **     it must fire another vetoableChange() event notifying the others
     **     of a reversion to the old value (though, of course, the change
     **     was never made).  Then it rethrows the PropertyVetoException and
     **     exits.</LI>
     ** <LI>If all has gone well to this point, the value may be changed.</LI>
     ** </OL>
     ** @param constrained whether the property is constrained or not.
     **/
    public void setConstrained(boolean constrained)
    {
        this.constrained = constrained;
    }

    /** Get the PropertyEditor class.  Defaults to null. **/
    public Class getPropertyEditorClass()
    {
        return propertyEditorClass;
    }

    /** Set the PropertyEditor class.  If the class does not implement
     ** the PropertyEditor interface, you will likely get an exception
     ** late in the game.
     ** @param propertyEditorClass the PropertyEditor class for this 
     **        class to use.
     **/
    public void setPropertyEditorClass(Class propertyEditorClass)
    {
        this.propertyEditorClass = propertyEditorClass;
    }

    private void findMethods(
        Class beanClass,
        String getMethodName1,
        String getMethodName2,
        String setMethodName)
        throws IntrospectionException
    {
        try
        {
            // Try the first get method name
            if (getMethodName1 != null)
            {
                try
                {
                    getMethod =
                        beanClass.getMethod(getMethodName1, new Class[0]);
                }
                catch (NoSuchMethodException e)
                {}
            }

            // Fall back to the second get method name
            if (getMethod == null && getMethodName2 != null)
            {
                try
                {
                    getMethod =
                        beanClass.getMethod(getMethodName2, new Class[0]);
                }
                catch (NoSuchMethodException e)
                {}
            }

            // Try the set method name
            if (setMethodName != null)
            {
                if (getMethod != null)
                {
                    // If there is a get method, use its return type to help
                    // select the corresponding set method.
                    Class propertyType = getMethod.getReturnType();
                    if (propertyType == Void.TYPE)
                    {
                        String msg =
                            "The property's read method has return type 'void'";
                        throw new IntrospectionException(msg);
                    }

                    Class[] setArgs = new Class[] { propertyType };
                    try
                    {
                        setMethod = beanClass.getMethod(setMethodName, setArgs);
                    }
                    catch (NoSuchMethodException e)
                    {}
                }
                else if (getMethodName1 == null && getMethodName2 == null)
                {
                    // If this is a write-only property, choose the first set method
                    // with the required name, one parameter and return type 'void'
                    Method[] methods = beanClass.getMethods();
                    for (int i = 0; i < methods.length; i++)
                    {
                        if (methods[i].getName().equals(setMethodName)
                            && methods[i].getParameterTypes().length == 1
                            && methods[i].getReturnType() == Void.TYPE)
                        {
                            setMethod = methods[i];
                            break;
                        }
                    }
                }
            }
        }
        catch (SecurityException e)
        {
            // FIXME -- shouldn't we just allow SecurityException to propagate?
            String msg =
                "SecurityException thrown on attempt to access methods.";
            throw new IntrospectionException(msg);
        }
    }

    /** Checks whether the given <code>Method</code> instances are legal read and
     * write methods. The following requirements must be met:<br/>
     * <ul>
     * <li>the read method must not have an argument</li>
     * <li>the read method must have a non void return type</li>
     * <li>the read method may not exist</li>
     * <li>the write method must have a single argument</li>
     * <li>the property type and the read method's return type must be assignable from the
     * write method's argument type</li>
     * <li>the write method may not exist</li>
     * </ul>
     * While checking the methods a common new property type is calculated. If the method
     * succeeds this property type is returned.<br/>
     * <br/>
     * For compatibility this has to be noted:<br/>
     * The two methods are allowed to be defined in two distinct classes and may both be null.
     * 
     * @param readMethod The new read method to check.
     * @param writeMethod The new write method to check.
     * @return The common property type of the two method.
     * @throws IntrospectionException If any of the above requirements are not met.
     */
    private Class checkMethods(Method readMethod, Method writeMethod)
        throws IntrospectionException
    {
        Class newPropertyType = propertyType;

        // a valid read method has zero arguments and a non-void return type.
        if (readMethod != null)
        {
            if (readMethod.getParameterTypes().length > 0)
            {
                throw new IntrospectionException("read method has unexpected parameters");
            }

            newPropertyType = readMethod.getReturnType();

            if (newPropertyType == Void.TYPE)
            {
                throw new IntrospectionException("read method return type is void");
            }
        }

        // a valid write method has one argument which can be assigned to the property
        if (writeMethod != null)
        {
            if (writeMethod.getParameterTypes().length != 1)
            {
                String msg = "write method does not have exactly one parameter";
                throw new IntrospectionException(msg);
            }

            if (readMethod == null)
            {
                // changes the property type if there is no read method
                newPropertyType = writeMethod.getParameterTypes()[0];
            }
            else
            {
                // checks whether the write method can be assigned to the return type of the read
                // method (if this is not the case, the methods are not compatible)
                // note: newPropertyType may be null if no methods or method names have been
                // delivered in the constructor.
                if (newPropertyType != null
                    && !newPropertyType.isAssignableFrom(
                        writeMethod.getParameterTypes()[0]))
                {
                    // note: newPropertyType is the same as readMethod.getReturnType() at this point
                    throw new IntrospectionException("read and write method are not compatible");
                }

                /* note: the check whether both method are defined in related classes makes sense but is not
                 * done in the JDK. 
                 * I leave this code here in case someone at Sun decides to add that functionality in later versions (rschuster)
                if ((!readMethod
                    .getDeclaringClass()
                    .isAssignableFrom(writeMethod.getDeclaringClass()))
                    && (!writeMethod
                        .getDeclaringClass()
                        .isAssignableFrom(readMethod.getDeclaringClass())))
                {
                    String msg =
                        "set and get methods are not in the same class.";
                    throw new IntrospectionException(msg);
                }
                */

            }
        }

        return newPropertyType;
    }

    /**
     * Return a hash code for this object, conforming to the contract described
     * in {@link Object#hashCode()}.
     * @return the hash code
     * @since 1.5
     */
    public int hashCode()
    {
      return ((propertyType == null ? 0 : propertyType.hashCode())
              | (propertyEditorClass == null ? 0 : propertyEditorClass.hashCode())
              | (bound ? Boolean.TRUE : Boolean.FALSE).hashCode()
              | (constrained ? Boolean.TRUE : Boolean.FALSE).hashCode()
              | (getMethod == null ? 0 : getMethod.hashCode())
              | (setMethod == null ? 0 : setMethod.hashCode()));
    }

    /** Compares this <code>PropertyDescriptor</code> against the
     * given object.
     * Two PropertyDescriptors are equals if
     * <ul>
     * <li>the read methods are equal</li>
     * <li>the write methods are equal</li>
     * <li>the property types are equals</li>
     * <li>the property editor classes are equal</li>
     * <li>the flags (constrained and bound) are equal</li>
     * </ul>
     * @return Whether both objects are equal according to the rules given above.
     * @since 1.4
    */
    public boolean equals(Object o)
    {
        if (o instanceof PropertyDescriptor)
        {
            PropertyDescriptor that = (PropertyDescriptor) o;

            // compares the property types and checks the case where both are null
            boolean samePropertyType =
                (propertyType == null)
                    ? that.propertyType == null
                    : propertyType.equals(that.propertyType);

            // compares the property editor classes and checks the case where both are null
            boolean samePropertyEditorClass =
                (propertyEditorClass == null)
                    ? that.propertyEditorClass == null
                    : propertyEditorClass.equals(that.propertyEditorClass);

            // compares the flags for equality
            boolean sameFlags =
                bound == that.bound && constrained == that.constrained;

            // compares the read methods and checks the case where both are null
            boolean sameReadMethod =
                (getMethod == null)
                    ? that.getMethod == null
                    : getMethod.equals(that.getMethod);

            boolean sameWriteMethod =
                (setMethod == null)
                    ? that.setMethod == null
                    : setMethod.equals(that.setMethod);

            return samePropertyType
                && sameFlags
                && sameReadMethod
                && sameWriteMethod
                && samePropertyEditorClass;
        }
        else
        {
            return false;
        }
        
    }

}