过滤HTML代码的函数，主要过虑用户上传的表单。-/*

* Copyright 2004 The Apache Software Foundation

*

* Licensed under the Apache License, Version 2.0 (the "License")

* you may not use this file except in compliance with the License.

* You may obtain a copy of the License at

*

*　　 http://www.apache.org/licenses/LICENSE-2.0

*

* Unless required by applicable law or agreed to in writing, software

* distributed under the License is distributed on an "AS IS" BASIS,

* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

* See the License for the specific language governing permissions and

* limitations under the License.

*/