Java 如何使用Jackson的ObjectMapper将下面的JSON转换为POJO

我试图在下面的代码中使用Jackson的ObjectMapper类将下面的JSON转换为POJO，但它引发了异常。谁能帮我解决这个问题。 实际上，JSON是由UI提供的，所以不能更改它的格式。我需要使用Jackson库将这个JSON解析为java对象

JSON:data.JSON

{
    "0": {
        "location": "6",
        "userType": "1",
        "isActive": "1",
        "userId": "Shailesh@gmail.com"
    },
    "1": {
        "location": "7",
        "userType": "2",
        "isActive": "1",
        "userId": "Vikram@gmail.com"
    }
}

DTOs:

public class UsersList {
    List<UserDetails> users;
}

public class UserDetails {
    private String userId;
    private String location;
    private String userType;
    private String isActive;

    public String getUserId() {
        return userId;
    }
    public void setUserId(String userId) {
        this.userId = userId;
    }
    public String getLocation() {
        return location;
    }
    public void setLocation(String location) {
        this.location = location;
    }
    public String getUserType() {
        return userType;
    }
    public void setUserType(String userType) {
        this.userType = userType;
    }
    public String getIsActive() {
        return isActive;
    }
    public void setIsActive(String isActive) {
        this.isActive = isActive;
    }
}

例外情况：

---

com.fasterxml.jackson.databind.JsonMappingException:由于输入结束，没有要映射的内容

JSON的格式是

映射

看看，键

0

有用户

”Shailesh@gmail.com“

和带有

的键
1
”Vikram@gmail.com“

然后将其映射到

UserDetails

 UserDetails sample = new ObjectMapper().readValue(instream, UsersList.class);

---

首先，在将json字符串反序列化为DTO之前，DTO应该不包含参数构造函数、getter和setter。 您当前的DTO将匹配如下所示的字符串

{
    "users": [
        {
            "location": "6",
            "userType": "1",
            "isActive": "1",
            "userId": "Shailesh@gmail.com"
        },
        {
            "location": "7",
            "userType": "2",
            "isActive": "1",
            "userId": "Vikram@gmail.com"
        }
    ]
}

与上面提供的字符串示例匹配的DTO如下所示

public class UsersList {
    UserDetails zero;
    UserDetails one;

    public UsersList() {
    }

    public UserDetails getZero() {
        return zero;
    }

    public void setZero(final UserDetails zero) {
        this.zero = zero;
    }

    public UserDetails getOne() {
        return one;
    }

    public void setOne(final UserDetails one) {
        this.one = one;
    }
}

---

您可以使用jackson的ObjectMapper.readValue（）方法

我认为您的解决方案如下：

    String jsonBody = yourJson;
    ObjectMapper objectMapper = new ObjectMapper();
    try {
        UserDetailsMapDao userDetailsMapDao = objectMapper
                .readValue(jsonBody, UserDetailsMapDao.class);
    } catch (JsonParseException e) {
        // TODO Exception Handling
    } catch (JsonMappingException e) {
        // TODO Exception Handling
    } catch (IOException e) {
        // TODO Exception Handling
    }

您的DAO将如下所示：

公共类UserDetailsMapDao{

private Map<String, UserDetails> userDetailsMap;

public String getUserDetailsMap() {
return userDetailsMap;
}
public void setUserDetailsMap(String userDetailsMap) {
this.userDetailsMap = userDetailsMap;
}

}

public class UsersList {
    UserDetails zero;
    UserDetails one;

    public UsersList() {
    }

    public UserDetails getZero() {
        return zero;
    }

    public void setZero(final UserDetails zero) {
        this.zero = zero;
    }

    public UserDetails getOne() {
        return one;
    }

    public void setOne(final UserDetails one) {
        this.one = one;
    }
}

    String jsonBody = yourJson;
    ObjectMapper objectMapper = new ObjectMapper();
    try {
        UserDetailsMapDao userDetailsMapDao = objectMapper
                .readValue(jsonBody, UserDetailsMapDao.class);
    } catch (JsonParseException e) {
        // TODO Exception Handling
    } catch (JsonMappingException e) {
        // TODO Exception Handling
    } catch (IOException e) {
        // TODO Exception Handling
    }

private Map<String, UserDetails> userDetailsMap;

public String getUserDetailsMap() {
return userDetailsMap;
}
public void setUserDetailsMap(String userDetailsMap) {
this.userDetailsMap = userDetailsMap;
}

private String userId;
private String location;
private String userType;
private String isActive;

public String getUserId() {
    return userId;
}
public void setUserId(String userId) {
    this.userId = userId;
}
public String getLocation() {
    return location;
}
public void setLocation(String location) {
    this.location = location;
}
public String getUserType() {
    return userType;
}
public void setUserType(String userType) {
    this.userType = userType;
}
public String getIsActive() {
    return isActive;
}
public void setIsActive(String isActive) {
    this.isActive = isActive;
}