数据交换格式（data-interchange format） JSON

前端JSON：
JavaScript中的JSON
http://www.dreamdu.com/blog/2008/10/19/json_in_javascript/
用 javascript 处理 JSON
http://jelly.iteye.com/blog/138707



后台Java JSON：
java json处理框架，目前比较好的（性能等考量）两个是jackson和gson。比较：
http://stackoverflow.com/questions/2378402/jackson-vs-gson在json-tools、jackson、gson等中，jackson的性能无疑是最好的，着重抓住它的API就行了。

JACKSON：
1 jackson Serialization：
http://stackoverflow.com/questions/5430524/serialization-of-key-value-pairs-in-jackson
2 Using jackson deserialize a jsonString to java nested object：
http://stackoverflow.com/questions/8921089/jackson-converting-json-property-to-nested-object-with-dot-notation
3 jsonString中的key，在对应的java entity中使用 @JsonProperty 注解 做对应。
4 对 non-static inner class，jackson 可以将其 serializable 序列化，但不可以 deserializable 反序列化一个 json 字符串给该 non-static inner class，详见：
http://jira.codehaus.org/browse/JACKSON-594
http://www.cowtowncoder.com/blog/archives/2010/08/entry_411.html
http://stackoverflow.com/questions/7144912/why-is-a-serializable-inner-class-not-serializable
5 @JsonCreator 。。。。。。。
老版本的jackson只能通过默认的无参构造方法
新的支持通过 @JsonCreator 来用有参构造方法来做反序列化(当同时没有无参构造方法被定义时尤其有用)，并且可以基于其对 enum 做反序列化：
。。。。。。。。
http://wiki.fasterxml.com/JacksonFeatureCreators
http://stackoverflow.com/questions/11838039/jackson-3rd-party-class-with-no-default-constructor
http://stackoverflow.com/questions/9300191/how-to-annotate-enum-fields-for-deserialization-using-jackson-json?rq=1
http://stackoverflow.com/questions/8790389/jackson-deserialize-one-base-enums

引用

例子：需要反序列化的类 CacheKey 的结构如下：

@JsonIgnoreProperties(ignoreUnknown=true)
public class CacheKey implements Serializable {

    private String key;
    private CacheType cacheType;

    public CacheKey(String key, CacheType cacheType) {
        Validate.notEmpty(key, "key of CacheKey must be not empty");
        Validate.notNull(cacheType, "cacheType of CacheKey must be not null");
        this.key = key;
        this.cacheType = cacheType;
    }
}

public enum CacheType {

    CACHE_TYPE_A("cache-type-a", 60*60*4), // caching 4 hours
    CACHE_TYPE_A("cache-type-b", 60*60*24); // caching 1 day

    private final String prefix; // prefix of cacheType's key
    private int exp; // default expire time in seconds

    private CacheType(String prefix, int exp) {
        this.prefix = prefix;
        this.exp = exp;
    }
}

方式一：Factory-based Creator(在类 CacheKey 中添加如下静态工厂方法并注解为@JsonCreator)：

public class CacheKey implements Serializable {
    @JsonCreator
    public static CacheKey fromValue(@JsonProperty("key") String key, @JsonProperty("type") String type) {

        CacheType cacheType = null;
        for (CacheType c: CacheType.values()) {
            if (c.getPrefix().equals(type)) {
                cacheType = c;
            }
        }

        if (null == cacheType) {
            throw new IllegalArgumentException("Invalid type of cache: " + type);
        }

        return new CacheKey(key, cacheType);
    }
}

方式二：Constructor-based Creator：

public class CacheKey implements Serializable {

    @JsonCreator
    public CacheKey(@JsonProperty("key") String key, @JsonProperty("type") CacheType cacheType) {
        Validate.notEmpty(key, "key of CacheKey must be not empty");
        Validate.notNull(cacheType, "cacheType of CacheKey must be not null");
        this.key = key;
        this.cacheType = cacheType;
    }
}

public enum CacheType {
    @JsonCreator
    public static CacheType fromPrefix(String prefix) {
        for (CacheType c: CacheType.values()) {
            if (c.getPrefix().equals(prefix)) {
                return c;
            }
        }
        throw new IllegalArgumentException("Invalid CacheType: [" + prefix +
                "]. Acceptable CacheType can be " +
                Arrays.asList(CacheType.values()));
    }
}

6 一个ObjectMapper的使用例子：

ObjectMapper  mapper=  new ObjectMapper();
		GetJSONData getJons = new GetJSONData();
		String json = getJons.getJsonString(urlPath);
		String jsonString = json.substring(json.indexOf("\"data\":") + 7,
				json.length() - 1);
		List<RequestsCount> someClassList =
			    mapper.readValue(jsonString, TypeFactory.defaultInstance().constructCollectionType(List.class, RequestsCount.class));