如何序列化列表< customobject>用gson？ [英] How do I serialize list<customobject> using gson ?

问题描述

大家好，

我有一个员工类：

 import java.util.List; 
公共类员工{
 private String name; 
私人弦乐专业; 
 private Integer profId; 
 private List< String>角色; 
 
 public String getName（）{
 return name; 
} 
 
 public void setName（String name）{
 this.name = name; 
} 
 
 public String getProfession（）{
 return profession; 
} 
 
 public void setProfession（String profession）{
 this.profession = profession; 
} 
 
 public Integer getProfId（）{
 return profId; 
} 
 
 public void setProfId（Integer profId）{
 this.profId = profId; 
} 
 
 public List< String> getRoles（）{
返回角色; 
} 
 
 public void setRoles（List< String> roles）{
 this.roles = roles; 
} 
 
 @Override 
 public String toString（）{
 String result = name +\ n+ profession +\ n
 + profId +\ n+ roles.toString（）; 
 
返回结果; 
} 
 
} 

我尝试为员工列表生成Json表示：

列表<员工> emps = new ArrayList<>（）; 
员工emp1 =新员工（）{
 {
 setName（Hassan）; 
 setProfession（医生）; 
 setProfId（52）; 
 setRoles（Arrays.asList（surgeon，nose））; 
}}; 
 
员工emp2 =新员工（）{
 {
 setName（Jack）; 
 setProfession（Developer）; 
 setProfId（52）; 
 setRoles（Arrays.asList（Java））; 
}}; 
 
员工emp3 =新员工（）{
 {
 setName（Safy）; 
 setProfession（Driver）; 
 setProfId（52）; 
 setRoles（Arrays.asList（Nice，Kind））; 
}}; 
 
 emps.add（emp1）; 
 emps.add（emp2）; 
 emps.add（emp3）; 
 Gson gson = new Gson（）; 
类型type = new TypeToken< List< Employee>>（）{}。getType（）; 
 String jsonString = gson.toJson（emps，type）; 

生成的jsonString =[null，null，null]



在调试emps List中有3名员工按预期进行，且没有一个是空的



怎样才能正常完成？



非常感谢！



我尝试了什么：



我搜索了，

所有答案都说我应该使用TypeToken声明我做的类型但没有结果，

解决方案

删除双括号初始化，请参见此处：什么是Java中的Double Brace初始化？ - 堆栈溢出 [ ^ ]。

Hello every one,
I have an Employee class :

import java.util.List;
public class Employee {
    private String name;
    private String profession;
    private Integer profId;
    private List<String> roles;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getProfession() {
        return profession;
    }

    public void setProfession(String profession) {
        this.profession = profession;
    }

    public Integer getProfId() {
        return profId;
    }

    public void setProfId(Integer profId) {
        this.profId = profId;
    }

    public List<String> getRoles() {
        return roles;
    }

    public void setRoles(List<String> roles) {
        this.roles = roles;
    }

    @Override
    public String toString() {
        String result = name + "\n" + profession + "\n"
                + profId + "\n" + roles.toString();

        return result;
    }

}

I try to generate a Json representation for a list of employees :

List<Employee> emps = new ArrayList<>();
Employee emp1 = new Employee(){
            {
                setName("Hassan");
                setProfession("doctor");
                setProfId(52);
                setRoles( Arrays.asList("surgeon" ,  "nose"));
            }};

        Employee emp2 = new Employee(){
            {
                setName("Jack");
                setProfession("Developer");
                setProfId(52);
                setRoles( Arrays.asList("Java" ));
            }};

        Employee emp3 = new Employee(){
            {
                setName("Safy");
                setProfession("Driver");
                setProfId(52);
                setRoles( Arrays.asList("Nice" , "Kind" ));
            }};

        emps.add(emp1);
        emps.add(emp2);
        emps.add(emp3);
Gson gson = new Gson();
Type type = new TypeToken<List<Employee>>(){}.getType();
String jsonString = gson.toJson(emps,type);

The resulting jsonString = "[null,null,null]"

in debug the emps List has the 3 employees as expected and none of them is null

How can this be properly done ?

Thanks very much!

What I have tried:

I searched,
all the answers said I should just use the TypeToken in declaring the type witch I did but with no result,

解决方案

Remove the double brace initializations, see here: What is Double Brace initialization in Java? - Stack Overflow[^].

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