概念 : 是一个能够将java对象序列化为JSON字符串,也能够将JSON字符串反序列化为java对象的框架。
工具类代码(先导入jackson-databind,lombok和日志依赖)
public class JsonUtils {
public static final ObjectMapper mapper = new ObjectMapper();
private static final Logger logger = LoggerFactory.getLogger(JsonUtils.class);
@Nullable
public static String toString(Object obj) {
if (obj == null) {
return null;
}
if (obj.getClass() == String.class) {
return (String) obj;
}
try {
return mapper.writeValueAsString(obj);
} catch (JsonProcessingException e) {
logger.error("json序列化出错:" + obj, e);
return null;
}
}
@Nullable
public static <T> T toBean(String json, Class<T> tClass) {
try {
return mapper.readValue(json, tClass);
} catch (IOException e) {
logger.error("json解析出错:" + json, e);
return null;
}
}
@Nullable
public static <E> List<E> toList(String json, Class<E> eClass) {
try {
return mapper.readValue(json, mapper.getTypeFactory().constructCollectionType(List.class, eClass));
} catch (IOException e) {
logger.error("json解析出错:" + json, e);
return null;
}
}
@Nullable
public static <K, V> Map<K, V> toMap(String json, Class<K> kClass, Class<V> vClass) {
try {
return mapper.readValue(json, mapper.getTypeFactory().constructMapType(Map.class, kClass, vClass));
} catch (IOException e) {
logger.error("json解析出错:" + json, e);
return null;
}
}
@Nullable
public static <T> T nativeRead(String json, TypeReference<T> type) {
try {
return mapper.readValue(json, type);
} catch (IOException e) {
logger.error("json解析出错:" + json, e);
return null;
}
}
}
使用 :
创建一个实体类
@AllArgsConstructor
@NoArgsConstructor
@Data
public class User{
private String name;
private Integer age;
}
对象转换成json字符串
public static void main(String[] args) {
User user = new User("张飞",21);
String userStr = JsonUtils.toString(user);
System.out.println(userStr);
/*
outPut :
{"name":"张飞","age":21}
*/
}
json字符串转换为javaBean
public static void main(String[] args) {
User user = new User("张飞",21);
String userStr = JsonUtils.toString(user);
User user1 = JsonUtils.toBean(userStr, User.class);
System.out.println(user1);
/*
outPut :
User(name=张飞, age=21)
*/
}
json字符串转换为list
public static void main(String[] args) {
String json = "[10,5,-5,23]";
List<Integer> integerList = JsonUtils.toList(json, Integer.class);
System.out.println(integerList);
/*
outPut :
[10, 5, -5, 23]
*/
}
json字符串转换为map
public static void main(String[] args) {
String json = "{\"name\": \"zhangsan\",\"age\": \"21\"}";
Map<String, String> map = JsonUtils.toMap(json, String.class, String.class);
System.out.println(map);
/*
outPut :
{name=zhangsan, age=21}
*/
}
复杂类型转换(转换的结果是List里边封装有Map)
public static void main(String[] args) {
String json = "[{\"name\": \"zhangsan\",\"age\": \"21\"},{\"name\": \"rose\",\"age\": \"20\"}]";
List<Map<String, String>> maps = nativeRead(json, new TypeReference<List<Map<String, String>>>() {
});
for (Map<String, String> map : maps) {
System.out.println(map);
}
/*
outPut :
{name=zhangsan, age=21}
{name=rose, age=20}
*/
}
本文地址:https://blog.csdn.net/zwq56693/article/details/107376383
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