关于集合
List<String>
java">List<String> list = duoMapper.selectName();[
"alice1",
"alice2",
"alice3",
"alice4",
"alice5",
"alice6",
"alice7",
"alice8",
"alice9",
"alice10"
]
List<UserInfo>
java">List<UserInfo> list = duoMapper.selectName();java">[{"id": null,"name": "alice1","age": 24,"email": null,"area": null},{"id": null,"name": "alice2","age": 27,"email": null,"area": null}
]Map<String,Object>
map格式必须是两个，而且只能查一条数据，key若重复，将覆盖value
java">Map<String,Object> map = duoMapper.selectName();select name,age from user_info limit 1
{
"name": "alice1",
"age": 24
}
LinkedHashMap是hashmap的子类，都属于map，数据格式一致
关于数组
java"> // 假设我们有一个整型数组int[] numbers = {1, 2, 3, 4, 5};// 使用for循环遍历数组并打印每个元素for (int i = 0; i < numbers.length; i++) {System.out.print(numbers[i]);}12345
二维的话，双层
java"> // 二维数组int[][] matrix = {{1, 2, 3},{4, 5, 6},{7, 8, 9}};// 外层循环遍历行for (int i = 0; i < matrix.length; i++) {// 内层循环遍历列for (int j = 0; j < matrix[i].length; j++) {System.out.print(matrix[i][j] + " ");}System.out.println(); // 每打印完一行数据后换行}1 2 3
4 5 6
7 8 9
没有任何符号包裹，裸数据
关于json
导入jar包
<dependency><groupId>com.alibaba</groupId><artifactId>fastjson</artifactId><version>1.2.33</version> </dependency>
JSONObject
一种键值对的集合，写法类似map，所以key重复，value被覆盖，只有一组
java"> JSONObject jsonObject = new JSONObject();jsonObject.put("aaa","111");jsonObject.put("bbb","222");System.out.println(jsonObject);{"aaa":"111","bbb":"222"}
JSONArray
一个
java"> JSONObject jsonObject = new JSONObject();jsonObject.put("aaa","111");jsonObject.put("bbb","222");JSONArray jsonArray = new JSONArray();jsonArray.add(jsonObject);System.out.println(jsonArray);[{"aaa":"111","bbb":"222"}]
多个
java"> JSONObject jsonObject = new JSONObject();jsonObject.put("aaa","111");jsonObject.put("bbb","222");JSONObject jsonObject2 = new JSONObject();jsonObject2.put("ccc","333");jsonObject2.put("ddd","444");JSONArray jsonArray = new JSONArray();jsonArray.add(jsonObject);jsonArray.add(jsonObject2);System.out.println(jsonArray);[{"aaa":"111","bbb":"222"},{"ccc":"333","ddd":"444"}]
关于json转换
array转json
java">JSONObject jsonObject3 = (JSONObject)jsonArray.get(i);
JSONObject jsonObject4 = jsonArray.getJSONObject(i);array转string
java"> @Testpublic void test3(){JSONObject jsonObject = new JSONObject();jsonObject.put("aaa","111");jsonObject.put("bbb","222");JSONArray jsonArray = new JSONArray();jsonArray.add(jsonObject);//array转stringString str = JSONObject.toJSONString(jsonArray, SerializerFeature.WriteMapNullValue);System.out.println(str);}[{"aaa":"111","bbb":"222"}]
json转string
java"> // 创建一个JSONObject对象JSONObject jsonObject = new JSONObject();jsonObject.put("name", "John Doe");jsonObject.put("age", 30);jsonObject.put("city", "New York");// 将JSONObject转换成字符串String jsonString = jsonObject.toString();// 输出转换后的字符串System.out.println(jsonString);{"city":"New York","name":"John Doe","age":30}
string转json
java"> String result = "{\"code\":200,\"message\":\"success\"}";JSONObject json = JSONObject.parseObject(result);System.out.println(json);{"code":200,"message":"success"}
如果String有多组数据
java">String str = "[{\"name\":\"Alice\",\"age\":20},{\"name\":\"Bob\",\"age\":30}]";JSONArray jsonArray = JSON.parseArray(str);System.out.println(jsonArray);[{"name":"Alice","age":20},{"name":"Bob","age":30}]
json转java对象
java"> String result = "{\"id\":200,\"name\":\"jogging\"}";JSONObject jsonObject = JSONObject.parseObject(result);UserInfo userInfo = JSON.parseObject(jsonObject.toString(), UserInfo.class);System.out.println(userInfo);UserInfo(id=200, name=jogging, age=null, email=null, area=null)
