如何将 JSON 字符串转换为 Java 对象列表? [英] How to convert JSON string into List of Java object?

问题描述

这是我的 JSON 数组:-

<预><代码>[{"firstName": "abc",姓氏":xyz"},{"firstName": "pqr",姓氏":str"}]

我的 String 对象中有这个.现在我想将它转换为 Java 对象并将其存储在 Java 对象列表中.例如在学生对象中.我正在使用以下代码将其转换为 Java 对象列表:-

ObjectMapper mapper = new ObjectMapper();StudentList studentList = mapper.readValue(jsonString, StudentList.class);

我的列表类是:-

public class StudentList {私人名单<学生>参与者列表 = 新的 ArrayList();//getter 和 setter}

我的学生对象是:-

class 学生 {字符串名字；字符串姓氏；//getter 和 setter}

我在这里遗漏了什么吗?我遇到以下异常:-

异常:com.fasterxml.jackson.databind.JsonMappingException:无法从 START_ARRAY 令牌中反序列化 com.aa.Student 的实例

解决方案

您要求 Jackson 解析 StudentList.告诉它解析一个List(学生).由于 List 是通用的，您通常会使用 类型参考

列表<学生>参与者JsonList = mapper.readValue(jsonString, new TypeReference<List<Student>>(){});

This is my JSON Array :-

[ 
    {
        "firstName" : "abc",
        "lastName" : "xyz"
    }, 
    {
        "firstName" : "pqr",
        "lastName" : "str"
    } 
]

I have this in my String object. Now I want to convert it into Java object and store it in List of java object. e.g. In Student object. I am using below code to convert it into List of Java object : -

ObjectMapper mapper = new ObjectMapper();
StudentList studentList = mapper.readValue(jsonString, StudentList.class);

My List class is:-

public class StudentList {

    private List<Student> participantList = new ArrayList<Student>();

    //getters and setters
}

My Student object is: -

class Student {

    String firstName;
    String lastName;

    //getters and setters
}

Am I missing something here? I am getting below exception: -

Exception : com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of com.aa.Student out of START_ARRAY token

解决方案

You are asking Jackson to parse a StudentList. Tell it to parse a List (of students) instead. Since List is generic you will typically use a TypeReference

List<Student> participantJsonList = mapper.readValue(jsonString, new TypeReference<List<Student>>(){});

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