introspectionhelper.java

java ant的源码！非常值得看的源码

    /**
     * creator - allows use of create/store external
     * to IntrospectionHelper.
     * The class is final as it has a private constructor.
     */
    public static final class Creator {
        private NestedCreator nestedCreator;
        private Object parent;
        private Project project;
        private Object nestedObject;
        private String polyType;

        /**
         * Creates a new Creator instance.
         * This object is given to the UnknownElement to create
         * objects for sub-elements. UnknownElement calls
         * create to create an object, the object then gets
         * configured and then UnknownElement calls store.
         * SetPolyType may be used to override the type used
         * to create the object with. SetPolyType gets called
         * before create.
         *
         * @param project the current project
         * @param parent  the parent object to create the object in
         * @param nestedCreator the nested creator object to use
         */
        private Creator(
            Project project, Object parent, NestedCreator nestedCreator) {
            this.project = project;
            this.parent = parent;
            this.nestedCreator = nestedCreator;
        }

        /**
         * Used to override the class used to create the object.
         *
         * @param polyType a ant component type name
         */
        public void setPolyType(String polyType) {
            this.polyType = polyType;
        }

        /**
         * Create an object using this creator, which is determined
         * by introspection.
         *
         * @return the created object
         */
        public Object create() {
            if (polyType != null) {
                if (!nestedCreator.isPolyMorphic()) {
                    throw new BuildException(
                        "Not allowed to use the polymorphic form"
                        + " for this element");
                }
                ComponentHelper helper =
                    ComponentHelper.getComponentHelper(project);
                nestedObject = helper.createComponent(polyType);
                if (nestedObject == null) {
                    throw new BuildException(
                        "Unable to create object of type " + polyType);
                }
            }
            try {
                nestedObject = nestedCreator.create(
                    project, parent, nestedObject);
                if (project != null) {
                    project.setProjectReference(nestedObject);
                }
                return nestedObject;
            } catch (IllegalAccessException ex) {
                throw new BuildException(ex);
            } catch (InstantiationException ex) {
                throw new BuildException(ex);
            } catch (IllegalArgumentException ex) {
                if (polyType != null) {
                    throw new BuildException(
                        "Invalid type used " + polyType);
                }
                throw ex;
            } catch (InvocationTargetException ex) {
                Throwable t = ex.getTargetException();
                if (t instanceof BuildException) {
                    throw (BuildException) t;
                }
                throw new BuildException(t);
            }
        }

        /**
         * @return the real object (used currently only
         *         for preset def).
         */
        public Object getRealObject() {
            return nestedCreator.getRealObject();
        }

        /**
         * Stores the nested element object using a storage method
         * determined by introspection.
         *
         */
        public void store() {
            try {
                nestedCreator.store(parent, nestedObject);
            } catch (IllegalAccessException ex) {
                throw new BuildException(ex);
            } catch (InstantiationException ex) {
                throw new BuildException(ex);
            } catch (IllegalArgumentException ex) {
                if (polyType != null) {
                    throw new BuildException(
                        "Invalid type used " + polyType);
                }
                throw ex;
            } catch (InvocationTargetException ex) {
                Throwable t = ex.getTargetException();
                if (t instanceof BuildException) {
                    throw (BuildException) t;
                }
                throw new BuildException(t);
            }
        }
    }

    /**
     * Internal interface used to create nested elements. Not documented
     * in detail for reasons of source code readability.
     */
    private abstract static class NestedCreator {
        private Method method; // the method called to add/create the nested element

        NestedCreator(Method m) {
            this.method = m;
        }
        Method getMethod() {
            return method;
        }
        boolean isPolyMorphic() {
            return false;
        }
        Object getRealObject() {
            return null;
        }
        abstract Object create(Project project, Object parent, Object child)
                        throws InvocationTargetException,
                               IllegalAccessException,
                               InstantiationException;
        void store(Object parent, Object child)
             throws InvocationTargetException,
                    IllegalAccessException,
                    InstantiationException {
            // DO NOTHING
        }
    }

    private class CreateNestedCreator extends NestedCreator {
        CreateNestedCreator(Method m) {
            super(m);
        }

        Object create(Project project, Object parent, Object ignore)
            throws InvocationTargetException, IllegalAccessException {
            return getMethod().invoke(parent, new Object[] {});
        }
    }

    /** Version to use for addXXX and addConfiguredXXX */
    private class AddNestedCreator extends NestedCreator {

        static final int ADD = 1;
        static final int ADD_CONFIGURED = 2;

        private Constructor constructor;
        private int behavior; // ADD or ADD_CONFIGURED

        AddNestedCreator(Method m, Constructor c, int behavior) {
            super(m);
            this.constructor = c;
            this.behavior = behavior;
        }

        boolean isPolyMorphic() {
            return true;
        }

        Object create(Project project, Object parent, Object child)
                throws InvocationTargetException,
                IllegalAccessException, InstantiationException {
            if (child == null) {
                child = constructor.newInstance(
                    (constructor.getParameterTypes().length == 0)
                    ? new Object[] {} : new Object[] {project});
            }
            if (child instanceof PreSetDef.PreSetDefinition) {
                child = ((PreSetDef.PreSetDefinition) child)
                    .createObject(project);
            }
            if (behavior == ADD) {
                istore(parent, child);
            }
            return child;
        }

        void store(Object parent, Object child)
                throws InvocationTargetException,
                IllegalAccessException, InstantiationException {
            if (behavior == ADD_CONFIGURED) {
                istore(parent, child);
            }
        }

        private void istore(Object parent, Object child)
                throws InvocationTargetException,
                IllegalAccessException, InstantiationException {
            getMethod().invoke(parent, new Object[] {child});
        }
    }

    /**
     * Internal interface used to setting element attributes. Not documented
     * in detail for reasons of source code readability.
     */
    private abstract static class AttributeSetter {
        private Method method; // the method called to set the attribute
        AttributeSetter(Method m) {
            this.method = m;
        }
        abstract void set(Project p, Object parent, String value)
                      throws InvocationTargetException,
                             IllegalAccessException,
                             BuildException;
    }

    /**
     * Clears the static cache of on build finished.
     */
    public static void clearCache() {
        HELPERS.clear();
    }

    /**
     *
     */
    private NestedCreator createAddTypeCreator(
        Project project, Object parent, String elementName)
        throws BuildException {
        if (addTypeMethods.size() == 0) {
            return null;
        }
        ComponentHelper helper = ComponentHelper.getComponentHelper(project);

        Object addedObject = null;
        Method addMethod = null;
        Class clazz = helper.getComponentClass(elementName);
        if (clazz == null) {
            return null;
        }
        addMethod = findMatchingMethod(clazz, addTypeMethods);
        if (addMethod == null) {
            return null;
        }
        addedObject = helper.createComponent(elementName);
        if (addedObject == null) {
            return null;
        }
        Object rObject = addedObject;
        if (addedObject instanceof PreSetDef.PreSetDefinition) {
            rObject = ((PreSetDef.PreSetDefinition) addedObject).createObject(
                project);
        }
        final Object nestedObject = addedObject;
        final Object realObject = rObject;

        return new NestedCreator(addMethod) {
            Object create(Project project, Object parent, Object ignore)
                    throws InvocationTargetException, IllegalAccessException {
                if (!getMethod().getName().endsWith("Configured")) {
                    getMethod().invoke(parent, new Object[] {realObject});
                }
                return nestedObject;
            }

            Object getRealObject() {
                return realObject;
            }

            void store(Object parent, Object child)
                    throws InvocationTargetException, IllegalAccessException,
                    InstantiationException {
                if (getMethod().getName().endsWith("Configured")) {
                    getMethod().invoke(parent, new Object[] {realObject});
                }
            }
        };
    }

    /**
     * Inserts an add or addConfigured method into
     * the addTypeMethods array. The array is
     * ordered so that the more derived classes
     * are first.
     * If both add and addConfigured are present, the addConfigured
     * will take priority.
     * @param method the <code>Method</code> to insert.
     */
    private void insertAddTypeMethod(Method method) {
        Class argClass = method.getParameterTypes()[0];
        for (int c = 0; c < addTypeMethods.size(); ++c) {
            Method current = (Method) addTypeMethods.get(c);
            if (current.getParameterTypes()[0].equals(argClass)) {
                if (method.getName().equals("addConfigured")) {
                    // add configured replaces the add method
                    addTypeMethods.set(c, method);
                }
                return; // Already present
            }
            if (current.getParameterTypes()[0].isAssignableFrom(
                            argClass)) {
                addTypeMethods.add(c, method);
                return; // higher derived
            }
        }
        addTypeMethods.add(method);
    }

    /**
     * Search the list of methods to find the first method
     * that has a parameter that accepts the nested element object.
     * @param paramClass the <code>Class</code> type to search for.
     * @param methods the <code>List</code> of methods to search.
     * @return a matching <code>Method</code>; null if none found.
     */
    private Method findMatchingMethod(Class paramClass, List methods) {
        Class matchedClass = null;
        Method matchedMethod = null;

        for (int i = 0; i < methods.size(); ++i) {
            Method method = (Method) methods.get(i);
            Class  methodClass = method.getParameterTypes()[0];
            if (methodClass.isAssignableFrom(paramClass)) {
                if (matchedClass == null) {
                    matchedClass = methodClass;
                    matchedMethod = method;
                } else {
                    if (!methodClass.isAssignableFrom(matchedClass)) {
                        throw new BuildException("ambiguous: types "
                            + matchedClass.getName() + " and "
                            + methodClass.getName() + " match "
                            + paramClass.getName());
                    }
                }
            }
        }
        return matchedMethod;
    }

    private String condenseText(final String text) {
        if (text.length() <= MAX_REPORT_NESTED_TEXT) {
            return text;
        }
        int ends = (MAX_REPORT_NESTED_TEXT - ELLIPSIS.length()) / 2;
        return new StringBuffer(text).replace(ends, text.length() - ends,
            ELLIPSIS).toString();
    }
}