Java & Android | Json和对象/集合互转

平时用到json格式的数据有很多,今天抽个空整理一下.放眼望去除了原生JSONObject. json框架基本就是Gson,Fastjson,Jackson常用的会比较多一些. 下面就分别整理了用着三个框架的json和对象/集合的互转

测试环境
java Eclipse maven project main test

使用框架
我用的maven项目,所以配置pom.xml文件,写入以下配置即可. 需要jar包导入的自行下载.

            
            com.alibaba    
            fastjson    
            1.1.41    
           

            
            org.codehaus.jackson    
            jackson-mapper-asl    
            1.9.13    
        

        
            com.google.code.gson
            gson
            2.3
        

Jackson

public static void jackson() {
        System.out.println("Jackson的使用: ");
        ObjectMapper mapper = new ObjectMapper();
        
        Person person = new Person();
        person.setId(1);
        person.setName("Roy");
        person.setPassword("Roy123");
        
        List persons = new ArrayList();
        Person person1 = null;
           for(int i = 0; i<2;i++) {
               person1 = new Person();
               person1.setId(i);
               person1.setName("Andy"+i);
               person1.setPassword("Andy123"+i);
               persons.add(person1);
           }
           
        try {
            System.out.println("对象转json: "+mapper.writeValueAsString(person));
            System.out.println("集合转json: "+mapper.writeValueAsString(persons));
            
            System.out.println("----------------------------------");
            System.out.println("格式化jsonObject: "+mapper.readValue(mapper.writeValueAsString(person), Person.class));
            System.out.println("格式化jsonListObject: "+mapper.readValue(mapper.writeValueAsString(persons), new TypeReference>() {}));
        } catch (JsonGenerationException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        
    }

使用jackson互转可以看出来很方便. jackson已经为我们封装好了ObjectMapper. 不管是对象还是集合数据用writeValueAsString就可以直接转成json. 那么格式化json也是一句话readValue.就可以了.
深入看底层代码,这里跑出了异常.所以我们在使用的时候也要捕捉这个异常.
所以在代码中可以看到有3个catch

jackson.png

Gson

public static void gson() {
        System.out.println("\n\nGson的使用: ");
        Gson gson = new Gson(); 
        Person person = new Person();
        person.setId(1);
        person.setName("Roy");
        person.setPassword("Roy123");
        List persons = new ArrayList();
        Person person1 = null;
           for(int i = 0; i<2;i++) {
               person1 = new Person();
               person1.setId(i);
               person1.setName("Andy"+i);
               person1.setPassword("Andy123"+i);
               persons.add(person1);
           }
            
        System.out.println("对象转json: "+gson.toJson(person));
        System.out.println("集合转json: "+gson.toJson(persons));
        
        System.out.println("----------------------------------");
        
        Person jsonObiect = gson.fromJson(gson.toJson(person), Person.class);
        List jsonListObject = gson.fromJson(gson.toJson(persons), new TypeToken>(){}.getType());
        System.out.println("格式化jsonObject: "+jsonObiect);
        System.out.println("格式化jsonListObject: "+jsonListObject);
    }

使用gson转json也是非常方便的. 直接tojson就好了.
格式化json直接fromJson. 这里要注意的是第二个参数要跟着你的内容走.实体类.class或是泛型集合.

FastJson

public static void fastJson() {
        System.out.println("\n\nFastJson的使用: ");
        Person person = new Person();
        person.setId(1);
        person.setName("Roy");
        person.setPassword("Roy123");
        List persons = new ArrayList();
        Person person1 = null;
           for(int i = 0; i<2;i++) {
               person1 = new Person();
               person1.setId(i);
               person1.setName("Andy"+i);
               person1.setPassword("Andy123"+i);
               persons.add(person1);
           }
           
        System.out.println("对象转json: "+JSON.toJSONString(person));
        System.out.println("集合转json: "+JSON.toJSONString(persons));
        System.out.println("----------------------------------");
        
        System.out.println("格式化jsonObject: "+JSON.parseObject(JSON.toJSONString(person),Person.class));
        System.out.println("格式化jsonListObject: "+JSON.parseArray(JSON.toJSONString(persons), Person.class));
    }

使用fastjson转json ,不管是对象还是集合都用JSON.toJSONString
但是需要注意的是.格式化json时,是有parseObject和parseArray的区分的.
只是在方法上的区分.第二个参数还是实体类.class

控制台打印信息

Jackson的使用: 
对象转json: {"id":1,"name":"Roy","password":"Roy123"}
集合转json: [{"id":0,"name":"Andy0","password":"Andy1230"},{"id":1,"name":"Andy1","password":"Andy1231"}]
----------------------------------
格式化jsonObject: Person [id=1, name=Roy, password=Roy123]
格式化jsonListObject: [Person [id=0, name=Andy0, password=Andy1230], Person [id=1, name=Andy1, password=Andy1231]]


Gson的使用: 
对象转json: {"id":1,"name":"Roy","password":"Roy123"}
集合转json: [{"id":0,"name":"Andy0","password":"Andy1230"},{"id":1,"name":"Andy1","password":"Andy1231"}]
----------------------------------
格式化jsonObject: Person [id=1, name=Roy, password=Roy123]
格式化jsonListObject: [Person [id=0, name=Andy0, password=Andy1230], Person [id=1, name=Andy1, password=Andy1231]]


FastJson的使用: 
对象转json: {"id":1,"name":"Roy","password":"Roy123"}
集合转json: [{"id":0,"name":"Andy0","password":"Andy1230"},{"id":1,"name":"Andy1","password":"Andy1231"}]
----------------------------------
格式化jsonObject: Person [id=1, name=Roy, password=Roy123]
格式化jsonListObject: [Person [id=0, name=Andy0, password=Andy1230], Person [id=1, name=Andy1, password=Andy1231]]