使用Jackson替代FastJson进行json字符串和对象的相互转换

秒速五厘米 2023-10-09 21:23 45阅读 0赞

### 一、背景 ###

在前后端分离的项目中，后端经常涉及到json与对象互转的场景。之前使用的是Fastjson，但是，因为技术选型的原因，选择了SpringBoot自带的Jackson。  
这篇文章就简单的介绍下如何使用Jackson来进行json和对象的相互转换

### 二、使用 ###

@Data
    @NoArgsConstructor
    @AllArgsConstructor
    public class Company {
        
        private String companyName;
        private List<WebSite> webSites;
    }

@Data
    @NoArgsConstructor
    @AllArgsConstructor
    public class WebSite {
        
        private String webSiteName;
        private List<User> users;
    }

@Data
    @NoArgsConstructor
    @AllArgsConstructor
    public class User {
        
        private String userId;
        private String username;
        private String password;
    }

#### 1.对象转json字符串Test ####

@Test
    public void testObject2Json2() {
        
        User user2 = new User("1","上海辟谣专属队","职业辟谣，不信谣，不传谣，呵呵");
        List<User> users = new ArrayList<>();
        users.add(user2);
        WebSite webSite = new WebSite();
        webSite.setWebSiteName("xxxxxx.com");
        webSite.setUsers(users);
        List<WebSite> webSites = new ArrayList<>();
        webSites.add(webSite);
        Company company = new Company();
        company.setCompanyName("yyyyyy");
        company.setWebSites(webSites);
        ObjectMapper objectMapper = new ObjectMapper();
        try {
        
            String jsonString = objectMapper.writeValueAsString(company);
            System.out.println(jsonString);
        } catch (JsonProcessingException e) {
        
            log.error("error: ", e);
        }
    }

输出：

{
        "companyName":"yyyyyy","webSites":[{
        "webSiteName":"xxxxxx.com","users":[{
        "userId":"1","username":"上海辟谣专属队","password":"职业辟谣，不信谣，不传谣，呵呵"}]}]}

#### 2.json字符串转对象 ####

##### ①json单字符串转单对象 #####

@Test
    public void testJson2Object() {
        
        String json = "{\"companyName\":\"yyyyyy\",\"webSites\":[" +
                "{\"webSiteName\":\"xxxxxx.com\",\"users\":[{\"userId\":\"1\",\"username\":\"上海辟谣专属队\",\"password\":\"职业辟谣，不信谣，不传谣，呵呵\"}]}" +
                "]}";
        ObjectMapper objectMapper = new ObjectMapper();
        try {
        
            Company company = objectMapper.readValue(json, Company.class);
            System.out.println(company.getWebSites().get(0).getUsers().get(0).getUsername());
        } catch (JsonProcessingException e) {
        
            log.error("error: ", e);
        }
    }

输出：

上海辟谣专属队

##### ②json数组字符串转list集合对象 #####

@Test
    public void testJsonArrayString2ObjectArray() {
        
        String json = "[" +
                "{\"userId\":\"1\",\"username\":\"上海带刀沪卫\",\"password\":\"带刀大佬\"}" +
                ",{\"userId\":\"1\",\"username\":\"上海辟谣专属队\",\"password\":\"职业辟谣，不信谣，不传谣，呵呵\"}" +
                "]";
        ObjectMapper objectMapper = new ObjectMapper();
        try {
        
            TypeReference<List<User>> typeReference = new TypeReference<List<User>>() {
        
            };
            List<User> list = objectMapper.readValue(json, typeReference);
            list.forEach(user -> {
        
                System.out.println(user.getUsername());
            });
        } catch (JsonProcessingException e) {
        
            log.error("error: ", e);
        }

注：为什么会由

有数组json的转换时，需要指定jackson反序列化为什么类型，而不是让它自主决定反序列化成什么类型，需要用到TypeReference。

输出：

上海带刀沪卫
    上海辟谣专属队

对多层嵌套同样适用

@Test
    public void testJsonArrayString2ObjectArray2() {
        
        String json = "[" +
                    "{" +
                    "\"companyName\":\"yyyyyy\",\"webSites\":[" +
                            "{\"webSiteName\":\"xxxxxx.com\",\"users\":[" +
                                "{\"userId\":\"1\",\"username\":\"上海辟谣专属队\",\"password\":\"职业辟谣，不信谣，不传谣，呵呵\"}" +
                                "]" +
                            "}" +
                        "]" +
                    "}" +
                "]";
        ObjectMapper objectMapper = new ObjectMapper();
        try {
        
            TypeReference<List<Company>> typeReference = new TypeReference<List<Company>>() {
        
            };
            List<Company> list = objectMapper.readValue(json, typeReference);
            list.forEach(company -> {
        
                System.out.println(company.getWebSites().get(0).getUsers().get(0).getUsername());
            });
        } catch (JsonProcessingException e) {
        
            log.error("error: ", e);
        }
    }

[更复杂的使用可以看这篇文章][Link 1]  
[想使用FastJson的可以看这篇文章][FastJson]

[Link 1]: https://www.mianshigee.com/note/detail/18677oyy/
[FastJson]: https://blog.csdn.net/qq_41861832/article/details/128209502