Question

Java对象

class B {
   private String attr;
/***** getters and setters *****/

} 

class A {
      private String attr1;
      private String attr2;
      private Map<String,B> attr3;

    /***** getters and setters *****/

}

Json对象

json = {attr1 :"val1", attr2 : "val2", attr3 : {attr : "val"}}

如何将json转换为java Object（类java包含Map作为属性类型）？

Answer 1

你可以使用Jackson来做到这一点：

//Create mapper instance
ObjectMapper mapper = new ObjectMapper();

//Usea a JSON string (exists other methos, i.e. you can get the JSON from a file)
String jsonString= "{'name' : 'test'}";

//JSON from String to Object
MyClass result= mapper.readValue(jsonString, MyClass .class);

Answer 2

您可以使用Gson库，如下所示：

// representation string for your Json object
String json = "{\"attr1\": \"val1\",\"attr2\": \"val2\",\"attr3\": {\"attr\": \"val\"}}"; 

Gson gson = new Gson();
A a = gson.fromJson(json, A.class);

Answer 3

创建一个类似于您的json结构的模型/ POJO，然后通过将json字符串放入json文件中，可以通过使用下面的简单代码（通过使用杰克逊相关性）来获取Java对象

ObjectMapper mapper = new ObjectMapper();
File inRulesFile = (new ClassPathResource(rulesFileName + ".json")).getFile();
List<Rule> rules = mapper.readValue(inRulesFile, new TypeReference<List<Rule>>() {
        });

Answer 4

@RunWith(SpringRunner.class)
@SpringBootTest
class PostSaveServiceTest {

    private static final String PATH_TO_JSON = "classpath:json/post-save";

    private static final String EXTENSION_JSON = ".json";

    @Test
    void setData() {

        ObjectMapper objectMapper = new ObjectMapper();

        Post post = runParseJsonFile(objectMapper);

        System.out.println(post);

    }



    private Post runParseJsonFile(ObjectMapper objectMapper) {

        File pathToFileJson = getPathToFileJson(PATH_TO_JSON + EXTENSION_JSON);

        Post post = null;

        try {
            post = objectMapper.readValue(pathToFileJson, Post.class);
        } catch (IOException e) {

            System.out.println("File didn't found : " + e);
       }

        return post;
    }


        private File getPathToFileJson(String path) {

        File pathToJson = null;

        try {

            pathToJson = ResourceUtils.getFile(path);

        } catch (IOException e) {
            e.printStackTrace();
        }


        return pathToJson;
    }
}

如何使用ObjectMapper将JSON转换为JAVA对象？

4 个答案: