扩展fastjson的SimplePropertyPreFilter，以过滤不需要序列化的属性

版权声明：本文为博主原创文章，但是你也可以随意转载。 https://blog.csdn.net/smartcore/article/details/80106538

java应用在进行系统间通信时，经常会使用json格式进行数据传输交换。利用alibaba fastjson（本文使用的是1.2.46），对象与json字符串的相互转换非常的便利。

但是，在对对象进行json序列化时，经常会出现以下的场景：对象的类是一个与数据库表相关的业务实体类，如以下实体类：

public class DiagramEntity {
    private String name;
    private String code;
    private int beginDate;
    private int endDate;
    private int flag;
    private String createId;
    private int createDate;

    // 访问器定义
}

其对应的数据库表字段如下：

字段名	类型
name	varchar(36)
code	varchar(36)
beginDate	Integer
endDate	Integer
flag	Integer
createId	varchar(36)
createDate	Integer

然而，在向客户端或者对手系统传输数据时，我们可能会在运行时选择性的进行某些属性的传输，比如对以上的类，仅需要传输name、code、beginDate、endDate，其余的属性不需要传输。遇到此种情况我们可以使用fastjson提供的com.alibaba.fastjson.serializer.SimplePropertyPreFilter类，创建一个此类的对象，然后利用其getExcludes()方法，添加不需要进行序列化的属性。

为了更加的方便使用过滤属性，本文对SimplePropertyPreFilter类进行了微小扩展，实现了SimplePropertyPreFilterEx类，在后者中增加了一个带三个参数的构造函数：

public SimplePropertyPreFilterEx(Class<?> clazz, String[] includeProperties, String[] excludeProperties);

以更方便的设置序列化时包含或者排除的属性。如以下使用：

@Test
public void testJsonExcludes() {
    SimplePropertyPreFilterEx objFilter = new SimplePropertyPreFilterEx(null, null,
            new String[] {"flag", "createId", "createDate"});

    DiagramEntity objMessage = new DiagramEntity();
    objMessage.setName("张三三");
    objMessage.setCode("X001");

    String strRet = JSON.toJSONString(objMessage, objFilter);
    System.out.println(strRet);
}

输出结果：

{"beginDate":0,"code":"X001","endDate":0,"name":"张三三"}

附：SimplePropertyPreFilterEx类定义示例：

package com.bn.zbase.message.util;

/**
 * Copyright 1999-2017 Alibaba Group.
 *
 * 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.
 */

import com.alibaba.fastjson.serializer.SimplePropertyPreFilter;
import java.util.Collections;

public class SimplePropertyPreFilterEx extends SimplePropertyPreFilter {
    public SimplePropertyPreFilterEx(String... includeProperties){
        super(null, includeProperties);
    }

    public SimplePropertyPreFilterEx(Class<?> clazz, String... includeProperties){
        super(clazz, includeProperties);
    }

    public SimplePropertyPreFilterEx(Class<?> clazz, String[] includeProperties, String[] excludeProperties) {
        super(clazz, includeProperties == null ? new String[0] : includeProperties);
        if (excludeProperties != null && excludeProperties.length > 0) {
            Collections.addAll(getExcludes(), excludeProperties);
        }
    }
}