摘要：是通過編程擴展的方式定制序列化。支持種，用于不同場景的定制序列化。數據格式過濾器該過濾器由提供，代碼實現運行結果查看數據的過濾結果，發現中的屬性也被過濾掉了，不符合需求。過濾器該自定義過濾器實現接口，實現根據層級過濾數據中的屬性。

SerializeFilter是通過編程擴展的方式定制序列化。Fastjson 支持6種 SerializeFilter，用于不同場景的定制序列化。

PropertyPreFilter：根據 PropertyName 判斷是否序列化

PropertyFilter：根據 PropertyName 和 PropertyValue 來判斷是否序列化

NameFilter：修改 Key，如果需要修改 Key，process 返回值則可

ValueFilter：修改 Value

BeforeFilter：序列化時在最前添加內容

AfterFilter：序列化時在最后添加內容

JSON 數據格式如下，需要過濾掉其中 "book" 的 "price" 屬性。

JSON數據格式：

{
  "store": {
    "book": [
      {
        "category": "reference",
        "author": "Nigel Rees",
        "title": "Sayings of the Century",
        "price": 8.95
      },
      {
        "category": "fiction",
        "author": "Evelyn Waugh",
        "title": "Sword of Honour",
        "price": 12.99
      }
    ],
    "bicycle": {
      "color": "red",
      "price": 19.95
    }
  },
  "expensive": 10
}

該過濾器由?Fastjson 提供，代碼實現：?

String json = "{"store":{"book":[{"category":"reference","author":"Nigel Rees","title":"Sayings of the Century","price":8.95},{"category":"fiction","author":"Evelyn Waugh","title":"Sword of Honour","price":12.99}],"bicycle":{"color":"red","price":19.95}},"expensive":10}";
SimplePropertyPreFilter filter = new SimplePropertyPreFilter();
filter.getExcludes().add("price");
JSONObject jsonObject = JSON.parseObject(json);
String str = JSON.toJSONString(jsonObject, filter);
System.out.println(str);

運行結果：

{
  "store": {
    "bicycle": {
      "color": "red"
    },
    "book": [
      {
        "author": "Nigel Rees",
        "category": "reference",
        "title": "Sayings of the Century"
      },
      {
        "author": "Evelyn Waugh",
        "category": "fiction",
        "title": "Sword of Honour"
      }
    ]
  },
  "expensive": 10
}

查看 JSON 數據的過濾結果，發現 "bicycle" 中的 "price" 屬性也被過濾掉了，不符合需求。

該自定義過濾器實現 PropertyPreFilter 接口，實現根據層級過濾 JSON 數據中的屬性。
擴展類：

/**
 * 層級屬性刪除
 * 
 * @author yinjianwei
 * @date 2017年8月24日 下午3:55:19
 *
 */
public class LevelPropertyPreFilter implements PropertyPreFilter {

    private final Class clazz;
    private final Set includes = new HashSet();
    private final Set excludes = new HashSet();
    private int maxLevel = 0;

    public LevelPropertyPreFilter(String... properties) {
        this(null, properties);
    }

    public LevelPropertyPreFilter(Class clazz, String... properties) {
        super();
        this.clazz = clazz;
        for (String item : properties) {
            if (item != null) {
                this.includes.add(item);
            }
        }
    }

    public LevelPropertyPreFilter addExcludes(String... filters) {
        for (int i = 0; i < filters.length; i++) {
            this.getExcludes().add(filters[i]);
        }
        return this;
    }

    public LevelPropertyPreFilter addIncludes(String... filters) {
        for (int i = 0; i < filters.length; i++) {
            this.getIncludes().add(filters[i]);
        }
        return this;
    }

    public boolean apply(JSONSerializer serializer, Object source, String name) {
        if (source == null) {
            return true;
        }

        if (clazz != null && !clazz.isInstance(source)) {
            return true;
        }

        // 過濾帶層級屬性（store.book.price）
        SerialContext serialContext = serializer.getContext();
        String levelName = serialContext.toString();
        levelName = levelName + "." + name;
        levelName = levelName.replace("$.", "");
        levelName = levelName.replaceAll("[d+]", "");
        if (this.excludes.contains(levelName)) {
            return false;
        }

        if (maxLevel > 0) {
            int level = 0;
            SerialContext context = serializer.getContext();
            while (context != null) {
                level++;
                if (level > maxLevel) {
                    return false;
                }
                context = context.parent;
            }
        }

        if (includes.size() == 0 || includes.contains(name)) {
            return true;
        }

        return false;
    }

    public int getMaxLevel() {
        return maxLevel;
    }

    public void setMaxLevel(int maxLevel) {
        this.maxLevel = maxLevel;
    }

    public Class getClazz() {
        return clazz;
    }

    public Set getIncludes() {
        return includes;
    }

    public Set getExcludes() {
        return excludes;
    }
}

代碼實現：

public static void main(String[] args) {
    String json = "{"store":{"book":[{"category":"reference","author":"Nigel Rees","title":"Sayings of the Century","price":8.95},{"category":"fiction","author":"Evelyn Waugh","title":"Sword of Honour","price":12.99}],"bicycle":{"color":"red","price":19.95}},"expensive":10}";
    JSONObject jsonObj = JSON.parseObject(json);
    LevelPropertyPreFilter propertyPreFilter = new LevelPropertyPreFilter();
    propertyPreFilter.addExcludes("store.book.price");
    String json2 = JSON.toJSONString(jsonObj, propertyPreFilter);
    System.out.println(json2);
}

運行結果：?

{
  "store": {
    "bicycle": {
      "color": "red",
      "price": 19.95
    },
    "book": [
      {
        "author": "Nigel Rees",
        "category": "reference",
        "title": "Sayings of the Century"
      },
      {
        "author": "Evelyn Waugh",
        "category": "fiction",
        "title": "Sword of Honour"
      }
    ]
  },
  "expensive": 10
}

查看 JSON 數據的過濾結果，實現了上面的需求。

參考：http://www.cnblogs.com/dirgo/...