Gson简单使用

待我称王封你为后i 2022-03-11 15:49 377阅读 0赞

### Gson工具类使用 ###

常用类：`JsonArray` `JsonElement` `JsonObject` `JsonParser` `TypeToken`

在线文档： [gson2.2 Api][]

### pom.xml ###

导入gson包

<dependency>
        <groupId>com.google.code.gson</groupId>
        <artifactId>gson</artifactId>
        <version>2.8.5</version>
    </dependency>

### 简单使用 ###

package com.commons.test;
    
    import com.google.gson.JsonArray;
    import com.google.gson.JsonElement;
    import com.google.gson.JsonObject;
    import com.google.gson.JsonParser;
    import com.google.gson.reflect.TypeToken;
    import com.tianbao.flights.core.commons.utils.GsonUtils;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.util.StringUtils;
    
    import java.util.ArrayList;
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;
    
    /** * @author Jiangcheng Xiang * * Gson使用demo */
    public class GsonTest { 
    
        private static final Logger logger = LoggerFactory.getLogger(GsonTest.class);
    
        public static void main(String[] args) { 
    
            // ---------------------解析json
            String json = "{\n" +
                    " \"cid\":\"whitescreen\",\n" +
                    " \"adultNumber\":1,\n" +
                    " \"itineraries\":[\n" +
                    " {\n" +
                    " \"departureCode\":\"YVR\",\n" +
                    " \"arrivalCode\":\"LXA\",\n" +
                    " \"departureDate\":\"20190309\"\n" +
                    " },\n" +
                    " {\n" +
                    " \"departureCode\":\"LXA\",\n" +
                    " \"arrivalCode\":\"YVR\",\n" +
                    " \"departureDate\":\"20190313\"\n" +
                    " }\n" +
                    " ],\n" +
                    " \"currency\":\"CNY\",\n" +
                    " \"status\":0,\n" +
                    " \"msg\":\"success\"\n" +
                    "}";
            if (StringUtils.hasText(json)) { 
                JsonParser parser = new JsonParser();
                // 转换为json
                JsonElement jsonElement = parser.parse(json);
                JsonObject jsonObject = jsonElement.getAsJsonObject();
                // 解析
                String cid = jsonObject.get("cid").getAsString();
                int adultNumber = jsonObject.get("adultNumber").getAsInt();
                JsonArray itineraries = jsonObject.get("itineraries").getAsJsonArray();
                logger.info("cid: [{}], adultNumber: [{}]", cid, adultNumber);
                logger.info("cid: [{}], itineraries: [{}], adultNumber: [{}]", cid, itineraries, adultNumber);
            }
    
            // ---------------封装一个json字符串
            JsonObject jsonStr = new JsonObject();
            jsonStr.addProperty("name", "shuaishuai");
            jsonStr.addProperty("id", "00001");
            logger.info("get json str: [{}]", jsonStr);
    
            // ---------------json字符串转数组 Map
            jsonToObject();
    
        }
    
        public static void jsonToObject() { 
            // list
            List<Person> persons = new ArrayList<>();
            Person person = new Person();
            person.setAge(1);
            person.setName("xxx");
            persons.add(person);
            Person person1 = new Person();
            person1.setAge(2);
            person1.setName("jjj");
            persons.add(person1);
    
            String personJson = GsonUtils.toJson(persons);
            List<Person> list = GsonUtils.fromJson(personJson, new TypeToken<ArrayList<Person>>() { 
            }.getType());
            logger.info("result [{}]", list);
    
            // map
            Map<String, String> map = new HashMap<>();
            map.put("name", "xjc");
            map.put("age", "20");
            String mapJson = GsonUtils.toJson(map);
            Map<String, String> result = GsonUtils.fromJson(mapJson, new TypeToken<Map<String, String>>() { 
            }.getType());
            logger.info("result [{}]", result);
        }
    }
    
    class Person { 
    
        private String name;
    
        private int age;
    
        public String getName() { 
            return name;
        }
    
        public void setName(String name) { 
            this.name = name;
        }
    
        public int getAge() { 
            return age;
        }
    
        public void setAge(int age) { 
            this.age = age;
        }
    }

### Gson工具类 ###

package com.commons.utils;
    
    import com.google.gson.*;
    import org.springframework.util.StringUtils;
    
    import java.lang.reflect.Type;
    import java.util.ArrayList;
    import java.util.List;
    
    public abstract class GsonUtils { 
        private static Gson gson = new Gson();
        private static Gson gsonShowNull = new GsonBuilder().serializeNulls().create();
    
        public static <T> T fromJson(String json, Class<T> classOfT) { 
            return gson.fromJson(json, classOfT);
        }
    
        public static <T> T fromJson(String json, Class<T> classOfT, Object adapter) { 
            if (adapter == null) { 
                Gson gson = new Gson();
                return gson.fromJson(json, classOfT);
            }
            Gson gson = new GsonBuilder().registerTypeAdapter(classOfT, adapter).create();
            return gson.fromJson(json, classOfT);
        }
    
        public static <T> T fromJson(String json, Type typeOfT) { 
            return gson.fromJson(json, typeOfT);
        }
    
        public static String toJson(Object object) { 
            if (object == null) { 
                return "";
            }
            return gson.toJson(object);
        }
    
        public static String toJsonShowNull(Object object) { 
            if (object == null) { 
                return "";
            }
            return gsonShowNull.toJson(object);
        }
    
        public static String prettyJson(String input) { 
            JsonParser parser = new JsonParser();
            JsonObject json = parser.parse(input).getAsJsonObject();
            Gson gson = new GsonBuilder().setPrettyPrinting().create();
            return gson.toJson(json);
        }
    
        public static String jsonArrayAsString(JsonArray jsonArray) { 
            List<String> strList = new ArrayList<>();
            for (JsonElement jsonElement : jsonArray) { 
               strList.add(jsonElement.getAsString());
            }
            return StringUtils.collectionToCommaDelimitedString(strList);
        }
    
        public static JsonElement toJsonElement(Object object) { 
            return gson.toJsonTree(object);
        }
    }

[gson2.2 Api]: http://tool.oschina.net/apidocs/apidoc?api=gson2.2.2