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SerializeFilter是通过编程扩展的方式定制序列化。Fastjson 支持6种 SerializeFilter，用于不同场景的定制序列化。

• PropertyPreFilter：根据 PropertyName 判断是否序列化

• PropertyFilter：根据 PropertyName 和 PropertyValue 来判断是否序列化

• NameFilter：修改 Key，如果需要修改 Key，process 返回值则可

• ValueFilter：修改 Value

• BeforeFilter：序列化时在最前添加内容

• AfterFilter：序列化时在最后添加内容

1. 需求

JSON 数据格式如下，需要过滤掉其中 "book" 的 "price" 属性。

JSON数据格式：

{"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
}

2. SimplePropertyPreFilter 过滤器

该过滤器由 Fastjson 提供，代码实现： 

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);

运行结果：

{"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 数据的过滤结果，发现 "bicycle" 中的 "price" 属性也被过滤掉了，不符合需求。

3. LevelPropertyPreFilter 过滤器

该自定义过滤器实现 PropertyPreFilter 接口，实现根据层级过滤 JSON 数据中的属性。
扩展类：

/*** 层级属性删除* * @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<String> includes = new HashSet<String>();private final Set<String> excludes = new HashSet<String>();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;}// 过滤带层级属性（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<String> getIncludes() {return includes;}public Set<String> getExcludes() {return excludes;}
}

代码实现：

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);
}

运行结果： 

{"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 数据的过滤结果，实现了上面的需求。

参考：http://www.cnblogs.com/dirgo/...