I can’t understand why deserialization doesn’t work.

public static String readUserFile(String titleFile) {
    String pathJSONFile = "src/main/resources/"   titleFile   ".json";
    ObjectMapper objectMapper = new ObjectMapper();
    File jsonFile = new File(pathJSONFile);
    UsersPajo[] usersPajos2= null;

    try {
        usersPajos2 = objectMapper.readValue(jsonFile, UsersPajo[].class);
        System.out.println("_usersPajos2___"   usersPajos2);
    } catch (JsonProcessingException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    String information = Arrays.toString(usersPajos2);

    try {
        usersPajo = objectMapper.readValue(information, UsersPajo.class);
    } catch (JsonProcessingException e) {
        e.printStackTrace();
    } 
    }

I've already tried various options, but it looks like I'm confused.Here is the mistake.

com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of 
`model.UsersPajo` out of START_ARRAY token
at [Source: (String)"[UsersPajo{website='hildegard.org', address=Address{zipcode='92998- 
3874', geo=Geo{lng='81.1496', lat='-37.3159'}, suite='Apt. 556', city='Gwenborough', 
street='Kulas Light'}, phone='1-770-736-8031 x56442', name='Leanne Graham', 
company=Company{bs='harness real-time e-markets', catchPhrase='Multi-layered client-server 
neural-net', name='Romaguera-Crona'}, id=1, email='[email protected]', username='Bret'}, 
UsersPajo{website='anastasia.net', address=Address{zipcode='90566-7771', 
geo=Geo{lng='-34.46"[truncated 3643 chars]; line: 1, column: 1]
at 

Here is the class model

public class UsersPajo{
private String website;
private Address address;
private String phone;
private String name;
private Company company;
private int id;
private String email;
private String username;

public String getWebsite(){
    return website;
}

public Address getAddress(){
    return address;
}

public String getPhone(){
    return phone;
}

public String getName(){
    return name;
}

public Company getCompany(){
    return company;
}

public int getId(){
    return id;
}

public String getEmail(){
    return email;
}

public String getUsername(){
    return username;
}

@Override
public String toString() {
    return "UsersPajo{"  
            "website='"   website   '\''  
            ", address="   address  
            ", phone='"   phone   '\''  
            ", name='"   name   '\''  
            ", company="   company  
            ", id="   id  
            ", email='"   email   '\''  
            ", username='"   username   '\''  
            '}';
         }
       }

My JSON file

[ {
 "id" : 1,
 "name" : "Leanne Graham",
 "username" : "Bret",
 "email" : "[email protected]",
  "address" : {
     "street" : "Kulas Light",
     "suite" : "Apt. 556",
     "city" : "Gwenborough",
     "zipcode" : "92998-3874",
     "geo" : {
     "lat" : "-37.3159",
     "lng" : "81.1496"
    }
   },
 "phone" : "1-770-736-8031 x56442",
 "website" : "hildegard.org",
 "company" : {
    "name" : "Romaguera-Crona",
    "catchPhrase" : "Multi-layered client-server neural-net",
    "bs" : "harness real-time e-markets"
   }
}, ...
]

I read information from a file and then write it into a string. After that, I want to get my java object from this line using desrialization. Tell me why desirialization does not work? What needs to be fixed

CodePudding user response：

The issue is the following lines of code:

try {
    usersPajo = objectMapper.readValue(information, UsersPajo.class);
} catch (JsonProcessingException e) {
    e.printStackTrace();
} 

The variable information contains the following:

[UsersPajo{website='hildegard.org', address=Address{zipcode='92998- 
3874', geo=Geo{lng='81.1496', lat='-37.3159'}, suite='Apt. 556', city='Gwenborough', 
street='Kulas Light'}, phone='1-770-736-8031 x56442', name='Leanne Graham', 
company=Company{bs='harness real-time e-markets', catchPhrase='Multi-layered client-server 
neural-net', name='Romaguera-Crona'}, id=1, email='[email protected]', username='Bret'}, 
UsersPajo{website='anastasia.net', address=Address{zipcode='90566-7771', 
geo=Geo{lng='-34.46"....

Which basically is the usersPajos2 mapped to a String. This obviously can't be deserialized into a single UsersPajo instance. So get rid of these lines of code and keep all others:

public static String readUserFile(String titleFile) {
    String pathJSONFile = "src/main/resources/"   titleFile   ".json";
    ObjectMapper objectMapper = new ObjectMapper();
    File jsonFile = new File(pathJSONFile);
    UsersPajo[] usersPajos2= null;

    try {
        usersPajos2 = objectMapper.readValue(jsonFile, UsersPajo[].class);
        System.out.println("_usersPajos2___"   usersPajos2);
    } catch (JsonProcessingException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    return Arrays.toString(usersPajos2);
}