JSON的三种解析方式

http://www.2cto.com/kf/201401/270452.html

一、什么是JSON？

JSON是一种取代XML的数据结构,和xml相比,它更小巧但描述能力却不差,由于它的小巧所以网络传输数据将减少更多流量从而加快速度。

JSON就是一串字符串 只不过元素会使用特定的符号标注。

{} 双括号表示对象

[] 中括号表示数组

"" 双引号内是属性或值

: 冒号表示后者是前者的值(这个值可以是字符串、数字、也可以是另一个数组或对象)

所以 {"name": "Michael"} 可以理解为是一个包含name为Michael的对象

而[{"name": "Michael"},{"name": "Jerry"}]就表示包含两个对象的数组

当然了,你也可以使用{"name":["Michael","Jerry"]}来简化上面一部,这是一个拥有一个name数组的对象

二、JSON解析之传统的JSON解析

1、生成JSOn字符串

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public static String createJsonString(String key, Object value) {
        JSONObject jsonObject = new JSONObject();
        jsonObject.put(key, value);
        return jsonObject.toString();
    }

2、解析JSON字符串

分为以下三种情况，一个JavaBean，一个List数组，一个嵌套Map的List数组：

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import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
 
import org.json.JSONArray;
import org.json.JSONObject;
 
import com.android.myjson.domain.Person;
 
/**
 * 完成对json数据的解析
 *
 */
public class JsonTools {
 
 
    public static Person getPerson(String key, String jsonString) {
        Person person = new Person();
        try {
            JSONObject jsonObject = new JSONObject(jsonString);
            JSONObject personObject = jsonObject.getJSONObject("person");
            person.setId(personObject.getInt("id"));
            person.setName(personObject.getString("name"));
            person.setAddress(personObject.getString("address"));
        } catch (Exception e) {
            // TODO: handle exception
        }
        return person;
    }
 
    public static List<person> getPersons(String key, String jsonString) {
        List<person> list = new ArrayList<person>();
        try {
            JSONObject jsonObject = new JSONObject(jsonString);
            // 返回json的数组
            JSONArray jsonArray = jsonObject.getJSONArray(key);
            for (int i = 0; i < jsonArray.length(); i++) {
                JSONObject jsonObject2 = jsonArray.getJSONObject(i);
                Person person = new Person();
                person.setId(jsonObject2.getInt("id"));
                person.setName(jsonObject2.getString("name"));
                person.setAddress(jsonObject2.getString("address"));
                list.add(person);
            }
        } catch (Exception e) {
            // TODO: handle exception
        }
        return list;
    }
 
    public static List<string> getList(String key, String jsonString) {
        List<string> list = new ArrayList<string>();
        try {
            JSONObject jsonObject = new JSONObject(jsonString);
            JSONArray jsonArray = jsonObject.getJSONArray(key);
            for (int i = 0; i < jsonArray.length(); i++) {
                String msg = jsonArray.getString(i);
                list.add(msg);
            }
        } catch (Exception e) {
            // TODO: handle exception
        }
        return list;
    }
 
    public static List<map<string, object="">> listKeyMaps(String key,
            String jsonString) {
        List<map<string, object="">> list = new ArrayList<map<string, object="">>();
        try {
            JSONObject jsonObject = new JSONObject(jsonString);
            JSONArray jsonArray = jsonObject.getJSONArray(key);
            for (int i = 0; i < jsonArray.length(); i++) {
                JSONObject jsonObject2 = jsonArray.getJSONObject(i);
                Map<string, object=""> map = new HashMap<string, object="">();
                Iterator<string> iterator = jsonObject2.keys();
                while (iterator.hasNext()) {
                    String json_key = iterator.next();
                    Object json_value = jsonObject2.get(json_key);
                    if (json_value == null) {
                        json_value = "";
                    }
                    map.put(json_key, json_value);
                }
                list.add(map);
            }
        } catch (Exception e) {
            // TODO: handle exception
        }
        return list;
    }
}</string></string,></string,></map<string,></map<string,></map<string,></string></string></string></person></person></person>

三、JSON解析之GSON

1、生成JSON字符串

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import com.google.gson.Gson;
 
public class JsonUtils {
 
    public static String createJsonObject(Object obj) {
        Gson gson = new Gson();
        String str = gson.toJson(obj);
        return str;
 
    }
}

二、解析JSON

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import java.util.ArrayList;
import java.util.List;
import java.util.Map;
 
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
 
;
public class GsonTools {
 
    public GsonTools() {
        // TODO Auto-generated constructor stub
    }
 
    /**
     * @param <t>
     * @param jsonString
     * @param cls
     * @return
     */
    public static <t> T getPerson(String jsonString, Class<t> cls) {
        T t = null;
        try {
            Gson gson = new Gson();
            t = gson.fromJson(jsonString, cls);
        } catch (Exception e) {
            // TODO: handle exception
        }
        return t;
    }
 
    /**
     * 使用Gson进行解析 List<person>
     *
     * @param <t>
     * @param jsonString
     * @param cls
     * @return
     */
    public static <t> List<t> getPersons(String jsonString, Class<t> cls) {
        List<t> list = new ArrayList<t>();
        try {
            Gson gson = new Gson();
            list = gson.fromJson(jsonString, new TypeToken<list<t>>() {
            }.getType());
        } catch (Exception e) {
        }
        return list;
    }
 
    /**
     * @param jsonString
     * @return
     */
    public static List<string> getList(String jsonString) {
        List<string> list = new ArrayList<string>();
        try {
            Gson gson = new Gson();
            list = gson.fromJson(jsonString, new TypeToken<list<string>>() {
            }.getType());
        } catch (Exception e) {
            // TODO: handle exception
        }
        return list;
    }
 
    public static List<map<string, object="">> listKeyMaps(String jsonString) {
        List<map<string, object="">> list = new ArrayList<map<string, object="">>();
        try {
            Gson gson = new Gson();
            list = gson.fromJson(jsonString,
                    new TypeToken<list<map<string, object="">>>() {
                    }.getType());
        } catch (Exception e) {
            // TODO: handle exception
        }
        return list;
    }
}
</list<map<string,></map<string,></map<string,></map<string,></list<string></string></string></string></list<t></t></t></t></t></t></t></person></t></t></t>


三、JSON解析之FastJSON

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import java.util.ArrayList;
import java.util.List;
import java.util.Map;
 
import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.TypeReference;
 
public class JsonTool {
 
    public static <t> T getPerson(String jsonstring, Class<t> cls) {
        T t = null;
        try {
            t = JSON.parseObject(jsonstring, cls);
        } catch (Exception e) {
            // TODO: handle exception
        }
        return t;
    }
 
    public static <t> List<t> getPersonList(String jsonstring, Class<t> cls) {
        List<t> list = new ArrayList<t>();
        try {
            list = JSON.parseArray(jsonstring, cls);
        } catch (Exception e) {
            // TODO: handle exception
        }
        return list;
    }
 
    public static <t> List<map<string, object="">> getPersonListMap1(
            String jsonstring) {
        List<map<string, object="">> list = new ArrayList<map<string, object="">>();
        try {
            list = JSON.parseObject(jsonstring,
                    new TypeReference<list<map<string, object="">>>() {
                    }.getType());
 
        } catch (Exception e) {
            // TODO: handle exception
        }
 
        return list;
    }
}</list<map<string,></map<string,></map<string,></map<string,></t></t></t></t></t></t></t></t>

总结：

JSON对于移动设备来说，尤其对于网络环境较差和流量限制的情况下，相对于XML格式的数据传输会更节省流量，传输效率更高。在这三种解析方式中FastJson是效率最高的，推荐使用。

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原文地址：https://www.cnblogs.com/leaven/p/5135624.html