GWT序列化 - 類沒有可實例化的子類型

Question

我想序列化這個對象（OperatorDTO），所以我可以使用RPC從我的服務器端發送它到客戶端。我已閱讀關於此主題的其他文章，但我不明白爲什麼我做的事情與其他人不同。

當我跑我的項目出現此錯誤

Compiling module edu.example.RPCExample 
     Computing all possible rebind results for 'edu.example.client.service.ExampleService' 
      Rebinding edu.example.client.service.ExampleService 
       Invoking generator com.google.gwt.user.rebind.rpc.ServiceInterfaceProxyGenerator 
        Generating client proxy for remote service interface 'edu.example.client.service.ExampleService' 
        [ERROR] 'edu.example.client.models.OperatorDTO' has no instantiable subtypes 
     [ERROR] Errors in 'edu/example/client/service/ExampleServiceClientImpl.java' 
      [ERROR] Line 18: Failed to resolve 'edu.example.client.service.ExampleService' via deferred binding 
     Unification traversed 16362 fields and methods and 1526 types. 1494 are considered part of the current module and 1494 had all of their fields and methods traversed. 
     [ERROR] Compiler returned false 
     [WARN] recompile failed 
     [WARN] continuing to serve previous version 

我不明白爲什麼我得到的錯誤「OperatorDTO沒有實例化亞型」當我實現io.serializable只有在課堂上使用基本的數據類型。在序列化時不允許我在類中使用什麼東西？

package edu.example.client.models; 
import java.io.Serializable; 

public final class OperatorDTO implements Serializable 
{ 
    private static final long serialVersionUID = 1L; 
    private final int ID_MINIMUM_VALUE = 11; 
    private final int ID_MAXIMUM_VALUE = 99; 
    private final int RANK_MINIMUM_VALUE = -1; 
    private final int RANK_MAXIMUM_VALUE = 1; 
    private final int NAME_MINIMUM_LENGTH = 2; 
    private final int PASSWORD_MINIMUM_LENGTH = 6; 
    private final int NUMBER_OF_SPECIAL_CHARACTERS = 3; 

    private int oprID; 
    private String oprNavn; 
    private String ini; 
    private String cpr; 
    private String password; 
    private int rank; 

public OperatorDTO(int oprID, String oprNavn, String ini, String cpr, String password, int rank) { 
     setOprID(oprID); 
     setName(oprNavn); 
     setIni(ini); 
     setCpr(cpr); 
     setPassword(password); 
     setRank(rank); 
    } 

    public OperatorDTO(int oprID, String oprNavn, String ini, String cpr, String password) { 
     setOprID(oprID); 
     setName(oprNavn); 
     setIni(ini); 
     setCpr(cpr); 
     setPassword(password); 
    } 

    public void setIni(String ini) { 
     this.ini = ini; 
    } 

    public String getIni() { 
     return this.ini; 
    } 

    public void setRank(int rank) { 
     if(rank >= RANK_MINIMUM_VALUE && rank <= RANK_MAXIMUM_VALUE) 
      this.rank = rank;kravende"); 
    } 

    public int getRank() { 
     return this.rank; 
    } 

    public void setOprID(int oprID) { 
     if(oprID >= ID_MINIMUM_VALUE && oprID <= ID_MAXIMUM_VALUE) 
      this.oprID = oprID; 
    } 

    public int getOprID() { 
     return this.oprID; 
    } 

    public void setName(String name) { 
     if(name != null) 
      if(name.length() >= NAME_MINIMUM_LENGTH) 
       this.oprNavn = name; 
    } 

    public void setCpr(String cpr) { 
     this.cpr = cpr; 
    } 

    public void setPassword(String password) { 
     if(valPass(password)) 
      this.password = password; 
    } 

    public String getName() { 
     return this.oprNavn; 
    } 

    public String getCpr() { 
     return this.cpr; 
    } 

    public String getPassword() { 
     return this.password; 
    } 

    private boolean valPass(String pass) { 
     if(pass.length() < PASSWORD_MINIMUM_LENGTH) 
      return false; 

     byte lowerCase = 0; 
     byte upperCase = 0; 
     byte digit = 0; 
     byte specialChar = 0; 
     char[] passChar = pass.toCharArray(); 

     for (char c : passChar) { 
      if(Character.isLowerCase(c)) 
       lowerCase = 1; 
      else if(Character.isUpperCase(c)) 
       upperCase = 1; 
      else if(Character.isDigit(c)) 
       digit = 1; 
      else if(c == 46 || c == 45 || c == 95 || c == 43 || c ==33 || c == 63 || c == 61) 
       specialChar = 1; 
      else 
       return false; 
     } 
     return (lowerCase + upperCase + digit + specialChar) >= NUMBER_OF_SPECIAL_CHARACTERS; 
    } 

    @Override 
    public String toString() { 
     return "OperatorDTO{" + "oprID=" + oprID + ", oprNavn=" + oprNavn + ", ini=" + ini + ", cpr=" + cpr + ", password=" + password + ", rank=" + rank + '}'; 
    } 
} 

感謝您的任何幫助提前！

Answer 1

GWT需要默認的構造函數。

請參閱http://www.gwtproject.org/doc/latest/tutorial/RPC.html#serialize