不能反序列化未知类型的数组使用gson w/java

Question

问题是数组中包含的数据类型直到运行时才会知道。我创建了一个测试用例来说明我的问题。一切工作正常，直到涉及到数组。

User user1 = new User(1, "one"); 
User user2 = new User(2, "two"); 

User [] users = {user1, user2}; 

Gson gson = new Gson(); 

// gson processing array of known a type. WORKS FINE 
// observe use of brackets [] 
String toJson = gson.toJson(users, User[].class); 
User [] newUsers = gson.fromJson(toJson, User[].class); 
for(User user : newUsers) { 
    System.out.println(user.toString()); 
} 

// gson processing using reflection for single user. WORKS FINE 
final Class<?> userType = Class.forName("com.abc.ws.GsonTest$User"); 
User user3 = new User(3, "three"); 
toJson = gson.toJson(user3, userType); 
Object newUser = gson.fromJson(toJson, userType); 
System.out.println(newUser.toString()); 

// gson processing using reflection for array of users. FAILS. 
toJson = gson.toJson(users, WHAT_TO_PASS_HERE?); // it should be something like: userType[].class but that won't compile 
Object newerUsers = gson.fromJson(toJson, WHAT_TO_PASS_HERE?); // it should be something like: userType[].class but that won't compile 
for(User user : newerUsers) { 
    System.out.println(user.toString()); 
} 

btw：下面是完整的代码。

package com.abc; 


import com.google.gson.Gson; 


public class GsonTest { 
    public static void main(String[] args) throws Exception { 
     GsonTest.go(); 
} 

    public static void go() throws Exception { 
     User user1 = new User(1, "one"); 
     User user2 = new User(2, "two"); 

     User [] users = {user1, user2}; 

     Gson gson = new Gson(); 

     // gson processing array of known a type. Works fine 
     // observe use of brackets [] 
     String toJson = gson.toJson(users, User[].class); 
     User [] newUsers = gson.fromJson(toJson, User[].class); 
     for(User user : newUsers) { 
      System.out.println(user.toString()); 
     } 

     // gson processing using reflection for single user. Works fine. 
     final Class<?> userType = Class.forName("com.abc.GsonTest$User"); 
     User user3 = new User(3, "three"); 
     toJson = gson.toJson(user3, userType); 
     Object newUser = gson.fromJson(toJson, userType); 
     System.out.println(newUser.toString()); 

     // gson processing using reflection for array of users. Fails. 

     toJson = gson.toJson(users, WHAT_TO_PASS_HERE?); // it should be something like: userType[].class but that won't compile 
     Object newerUsers = gson.fromJson(toJson, WHAT_TO_PASS_HERE?); // it should be something like: userType[].class but that won't compile 
     for(User user : newerUsers) { 
      System.out.println(user.toString()); 
     } 
    } 

    public static class User { 
     private int id; 
     private String name; 

     public User() { } 

     public User(int id, String name) { 
      this.id = id; 
      this.name = name; 
     } 

     public int getId() { 
      return id; 
     } 

     public void setId(int id) { 
      this.id = id; 
     } 

     public String getName() { 
      return name; 
     } 

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

     public String toString() { 
      return "id: " + this.id + ", name: " + this.name; 
     } 
    } 
} 

Answer 1

尝试通

Array.newInstance(userType, 0).getClass() 

Answer 2

// serialized 
import java.beans.XMLDecoder; 
import java.beans.XMLEncoder; 
import java.io.FileInputStream; 
import java.io.FileOutputStream; 
import java.util.ArrayList; 


public class Serialization { 


    private ArrayList<Student> obj; 
    public Serialization() { 
     obj = new ArrayList<Student>(); 
     obj.add(new Student("qwrr", "qwerr", "qwerr")); 
     obj.add(new Student("zxcv", "zxcv", "zxcv")); 
     obj.add(new Student("asdf", "asdf", "asdf")); 
    } 

    public void Save() throws Exception{ 

     FileOutputStream os = new FileOutputStream("cust.xml"); 
     XMLEncoder encoder = new XMLEncoder(os); 
     encoder.writeObject(this.obj); 
     encoder.close(); 
    } 

    @SuppressWarnings("unchecked") 
    public ArrayList<Student> Load() throws Exception{ 
     FileInputStream os = new FileInputStream("cust.xml"); 
     XMLDecoder decoder = new XMLDecoder(os); 
     ArrayList<Student> p = (ArrayList<Student>)decoder.readObject(); 
     decoder.close(); 
     return p; 
    } 

    public static void main(String[] args) throws Exception { 

     Serialization obj = new Serialization(); 
     obj.Save(); 
     ArrayList<Student> mas = obj.Load(); 
     for(Student st:mas) 
     System.out.println(st); 

    } 

} 
// student 
public class Student { 

    private String firstName; 
    private String lastName; 
    private String location; 

    public Student(){ 

    } 

    public Student(String first,String last, String location) { 
     this.firstName = first; 
     this.lastName = last; 
     this.location = location; 
    } 

    public void setFirstName(String firstName) { 
     this.firstName = firstName; 
    } 

    public String getFirstName() { 
     return firstName; 
    } 

    public void setLastName(String lastName) { 
     this.lastName = lastName; 
    } 

    public String getLastName() { 
     return lastName; 
    } 

    public void setLocation(String location) { 
     this.location = location; 
    } 

    public String getLocation() { 
     return location; 
    } 

    @Override 
    public String toString(){ 
     return this.firstName+" "+this.lastName+" "+this.location; 
    } 

} 
//