json的解析问题

Myth丶恋晨 2022-03-29 12:56 376阅读 0赞

此博文以下列的json数据为例，讲解json转换或解析经常遇到的问题。

{ 
    	"success": true,
    	"resultMessage": "",
    	"result": [{ 
    		"code": "01",
    		"level": 1,
    		"orderSort": 1,
    		"pcode": "0",
    		"name": "配件",
    		"isleaf": 0,
    		"attrs": [{ 
    			"param_code": "01",
    			"sku": null,
    			"param_name": "支腿",
    			"param_value": "0-1000个",
    			"params_type": 0,
    			"unit": "个",
    			"sort": 1,
    			"type": 0,
    			"category_group": "结构件",
    			"group_sort": 3,
    			"note": "配件类型中的支腿"
    		}, { 
    			"param_code": "02",
    			"sku": null,
    			"param_name": "主电缆",
    			"param_value": "0-100米",
    			"params_type": 0,
    			"unit": "米",
    			"sort": 2,
    			"type": 0,
    			"category_group": "电气件",
    			"group_sort": 3,
    			"note": "配件类型中的主电缆"
    		}]
    	}],
    	"resultCode": "5000"
    }

此json数据涉及三个实体类,由外到内的顺序分别是  
JsonRootBean–>Attrs–>Result

JsonRootBean.java

/** * Copyright 2019 bejson.com */
    package com.besjon.pojo;
    import java.util.List;
    
    /** * Auto-generated: 2019-01-08 17:30:27 * * @author bejson.com (i@bejson.com) * @website http://www.bejson.com/java2pojo/ */
    public class JsonRootBean { 
    
        private boolean success;
        private String resultMessage;
        private List<Result> result;
        private String resultCode;
        public void setSuccess(boolean success) { 
             this.success = success;
         }
         public boolean getSuccess() { 
             return success;
         }
    
        public void setResultMessage(String resultMessage) { 
             this.resultMessage = resultMessage;
         }
         public String getResultMessage() { 
             return resultMessage;
         }
    
        public void setResult(List<Result> result) { 
             this.result = result;
         }
         public List<Result> getResult() { 
             return result;
         }
    
        public void setResultCode(String resultCode) { 
             this.resultCode = resultCode;
         }
         public String getResultCode() { 
             return resultCode;
         }
    
    }

Attrs.java

/** * Copyright 2019 bejson.com */
    package com.besjon.pojo;
    
    /** * Auto-generated: 2019-01-08 17:30:27 * * @author bejson.com (i@bejson.com) * @website http://www.bejson.com/java2pojo/ */
    public class Attrs { 
    
        private String param_code;
        private String sku;
        private String param_name;
        private String param_value;
        private int params_type;
        private String unit;
        private int sort;
        private int type;
        private String category_group;
        private int group_sort;
        private String note;
        public void setParam_code(String param_code) { 
             this.param_code = param_code;
         }
         public String getParam_code() { 
             return param_code;
         }
    
        public void setSku(String sku) { 
             this.sku = sku;
         }
         public String getSku() { 
             return sku;
         }
    
        public void setParam_name(String param_name) { 
             this.param_name = param_name;
         }
         public String getParam_name() { 
             return param_name;
         }
    
        public void setParam_value(String param_value) { 
             this.param_value = param_value;
         }
         public String getParam_value() { 
             return param_value;
         }
    
        public void setParams_type(int params_type) { 
             this.params_type = params_type;
         }
         public int getParams_type() { 
             return params_type;
         }
    
        public void setUnit(String unit) { 
             this.unit = unit;
         }
         public String getUnit() { 
             return unit;
         }
    
        public void setSort(int sort) { 
             this.sort = sort;
         }
         public int getSort() { 
             return sort;
         }
    
        public void setType(int type) { 
             this.type = type;
         }
         public int getType() { 
             return type;
         }
    
        public void setCategory_group(String category_group) { 
             this.category_group = category_group;
         }
         public String getCategory_group() { 
             return category_group;
         }
    
        public void setGroup_sort(int group_sort) { 
             this.group_sort = group_sort;
         }
         public int getGroup_sort() { 
             return group_sort;
         }
    
        public void setNote(String note) { 
             this.note = note;
         }
         public String getNote() { 
             return note;
         }
    
    }

Result.java

/** * Copyright 2019 bejson.com */
    package com.besjon.pojo;
    import java.util.List;
    
    /** * Auto-generated: 2019-01-08 17:30:27 * * @author bejson.com (i@bejson.com) * @website http://www.bejson.com/java2pojo/ */
    public class Result { 
    
        private String code;
        private int level;
        private int orderSort;
        private String pcode;
        private String name;
        private int isleaf;
        private List<Attrs> attrs;
        public void setCode(String code) { 
             this.code = code;
         }
         public String getCode() { 
             return code;
         }
    
        public void setLevel(int level) { 
             this.level = level;
         }
         public int getLevel() { 
             return level;
         }
    
        public void setOrderSort(int orderSort) { 
             this.orderSort = orderSort;
         }
         public int getOrderSort() { 
             return orderSort;
         }
    
        public void setPcode(String pcode) { 
             this.pcode = pcode;
         }
         public String getPcode() { 
             return pcode;
         }
    
        public void setName(String name) { 
             this.name = name;
         }
         public String getName() { 
             return name;
         }
    
        public void setIsleaf(int isleaf) { 
             this.isleaf = isleaf;
         }
         public int getIsleaf() { 
             return isleaf;
         }
    
        public void setAttrs(List<Attrs> attrs) { 
             this.attrs = attrs;
         }
         public List<Attrs> getAttrs() { 
             return attrs;
         }
    
    }

现在我们需要对这串json数据进行解析：

**将字符串转换成JSONObject对象**  
核心代码：

String json="{\"param_code\":\"01\",\"sku\":null,\"param_name\":\"支腿\",\"param_value\":\"0-1000个\",\"params_type\":0,\"unit\":\"个\",\"sort\":1,\"type\":0,\"category_group\":\"结构件\",\"group_sort\":3,\"note\":\"配件类型中的支腿\"}";
    JSONObject jsonObject =JSONObject.fromObject(json);
    System.out.println(jsonObject);

运行控制台输出：

{ "param_code":"01","sku":null,"param_name":"支腿","param_value":"0-1000个","params_type":0,"unit":"个","sort":1,"type":0,"category_group":"结构件","group_sort":3,"note":"配件类型中的支腿"}

**将字符串转换成JSONArray对象**  
核心代码：

String json="[{\"param_code\":\"01\",\"sku\":null,\"param_name\":\"支腿\",\"param_value\":\"0-1000个\",\"params_type\":0,\"unit\":\"个\",\"sort\":1,\"type\":0,\"category_group\":\"结构件\",\"group_sort\":3,\"note\":\"配件类型中的支腿\"}]";
    JSONArray jsonArray = JSONArray.fromObject(json);
    System.out.println(jsonArray);

运行控制台输出：

[{ "param_code":"01","sku":null,"param_name":"支腿","param_value":"0-1000个","params_type":0,"unit":"个","sort":1,"type":0,"category_group":"结构件","group_sort":3,"note":"配件类型中的支腿"}]

**将字符串快速转换为Json对象**  
传统json拼接：

String areaJson="{\"id\": \"01\", \t\"level\": \"2\", \t\"pid\": \"0\", \t\"name\": \"永州\" }";
    jsonObject jsonObject=JSONObject.fromObject(areaJson);

高效率拼接方式：

Area a=new Area();
    a.setId("02");
    a.setLevel(2);
    a.setPid("0");
    a.setName("上海");
    //转换为json对象
    Map<String,Object> map=new HashMap();
    map.put("id",a.getId());
    map.put("name",a.getName());
    map.put("pid",a.getPid());
    map.put("level",a.getLevel());
    jsonObject jsonObject=JSONObject.fromObject(map);
    //转换为json数组
    List<Map<String,Object>> list=new ArrayList<>();
    Map<String,Object> map1=new HashMap();
    map.put("id",a.getId());
    map.put("name",a.getName());
    map.put("pid",a.getPid());
    map.put("level",a.getLevel());
    Map<String,Object> map2=new HashMap();
    map2.put("id",a.getId());
    map2.put("name",a.getName());
    map2.put("pid",a.getPid());
    map2.put("level",a.getLevel());
    JSONArray jsonObject=JSONArray.fromObject(list);

**将JSONObject、JSONArray变为字符串**  
核心代码：

String str=jsonObject.toString();
    String str=jsonArray.toString();

**向JSONObject存放键和值**

核心代码：

JSONObject jsonObject = new JSONObject();
    jsonObject.put("name", "张三");
    System.out.println(jsonObject1.toString());

**将Collection对象转换成JSONArray对象, 本例为ArrayList**

核心代码：

List<String> list = new ArrayList<String>();
    list .add("uname");
    list .add("upwd");
    JSONArray jsonArray= JSONArray.fromObject(list );
    System.out.println(jsonArray);

**Map对象转换成JSONObject对象**  
核心代码：

Map<String, List<String>> map = new LinkedHashMap<String, List<String>>();
    List<String> list = new ArrayList<String>();
    list.add("student1");
    list.add("student2");
    map.put("teacher", list);
    JSONObject jsonObject = JSONObject.fromObject(map);
    System.out.println(jsonObject);

运行控制台输出：

{ "teacher":["student1","student2"]}

**将json数据中，值为数组的转换为List集合，以获取本文案例result键为例**

//解析的对象数组
    List objectList = new ArrayList<>();
    JSONArray object_json = result_json.getJSONArray("result");
    
    if (object_json.size() != 0) {  //保存所有的数组，数组如果为空数组为数组将不能进行更新
        //将Json数组转换为json对象
        JSONObject jsonObject;
        Object obj;
        for (int i = 0; i < object_json.size(); i++) { 
            jsonObject = JSONObject.fromObject(object_json.get(i).toString());
            obj = (Object) JSONObject.toBean(jsonObject, object.getClass());
            objectList.add(obj);
        }
    
    }

**列举JSONObject获取值的返回类型**

//假设jsonObject是有数据的
    JSONObject jsonObject = new JSONObject();
    
    String uname = jsonObject.getString("uname");
    boolean isDisabled = jsonObject.getBoolean("isDisabled");
    double price = jsonObject.getDouble("price");
    int age = jsonObject.getInt("age");
    Object obj = jsonObject.getJSONObject("person");
    Long l = jsonObject.getLong("price");

**判断json数据是json对象还是json数组**

//模拟JSONObject数据
    String object_json ="{\"scm\":{\"key1\":\"vlaue1\",\"key2\":\"vlaue2\"}}";
    //模拟JSONArray数据
    String array_json = "{\"scm\":[{\"key1\":\"vlaue1\",\"key2\":\"vlaue2\"},{\"key3\":\"vlaue3\",\"key4\":\"vlaue4\"}]}";
    //转换为json数据
    JSONObject json = JSONObject.fromObject(array_json);
    
    //通过scm键获取值
    Object obj = new JSONTokener(json.getString("scm")).nextValue();
     if (obj instanceof JSONObject) {  //json数据为JSONObject
        System.out.println("json为JSONObject");
        JSONObject jsonObject = (JSONObject) obj;
        System.out.println(jsonObject);
    
    }
     if (obj instanceof JSONArray) {  //json数据为JSONArray
        System.out.println("json为JSONArray");
        JSONArray jsonArray = (JSONArray) obj;
        for (int  i= 0;  i< jsonArray.size(); i++) { 
            JSONObject parameterObject = jsonArray.getJSONObject(i);
            System.out.println(parameterObject);
        }
    }

**注意**：  
1）net.sf.json.JSONObject

JSONObject是一个无序的键值对集合。值可以是任意类型：Boolean,JSONArray,JSONObject,Number,String,or the JSONObject.NULL Object

2）net.sf.json.JSONArray

JSONArray是一个有序的值序列。值可以是任意类型：Boolean, JSONArray, JSONObject, Number, String, or the JSONNull object。

3）JSONObject添加成员的方法element()与put()的区别:

put添加新成员：key是Object对象，value是Object对象  
element添加新成员：key是String对象，value是JSONObject对象

4）关于json数据嵌套的，例如对象中套数组，数组中的对象信息又套数组，不管怎样变化，由外到内，依次转换为json的键所对应的对象，所以并不困难，重要的是对json数据的分析

**博主整理了经常使用的，欢迎补充和斧正~**

**说在最后的话：编写实属不易，若喜欢或者对你有帮助记得点赞+关注或者收藏哦~**