java - 标识符 userName 未解析(不是静态字段)<有时>

Question

我正在使用 JDO 使对象持久化。我已经多次运行代码。有时，我会毫无错误地坚持下去。有时，我收到以下错误。

 1. org.datanucleus.exceptions.NucleusUserException
 2. javax.jdo.JDOUserException

我不明白为什么有时运行成功有时失败。这些都是随机发生的。我的应用程序在注册期间验证新用户。这是我的代码。

User.java(实体被持久化)

 @Entity
 @PersistenceCapable

 public class User {

@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
public String userName;

@Persistent
private String name, password, city, bikeModel, age;

public User(){

}
public User(String name, String uname, String pswd, String age, String city, String bike){
    this.name=name;
    this.userName=uname;
    this.password=pswd;
    this.age=age;
    this.city=city;
    this.bikeModel=bike;
}

public String getUserName() {
    return userName;
}
//rest of the getters
}

主要 servlet:

    //Getting SignUp form values
    String name=req.getParameter("name1");
    String uname=req.getParameter("uname1");
    String pswd=req.getParameter("pswd1");
    String age=req.getParameter("age");
    String city=req.getParameter("city");
    String bike=req.getParameter("bike");

            //PeristenceManager instance
            PersistenceManager pm = PMF.get().getPersistenceManager();

            //Creating instance for persistent entity class
     User newEntry=new User(name,uname,pswd,age,city,bike);

            //Query to match the userName entered in form and that of the dataStore user
    Query q = pm.newQuery(User.class);
    q.setFilter("userName == userNameParam");
    q.declareParameters("String userNameParam");
            try{
      List<User> results = (List<User>) q.execute(uname);
      if (!results.isEmpty()) {
                //if userName is found in DataStore
            resp.sendRedirect("invalidUser.html");  
      } else{
             //If userName is not found in dataStore
          pm.makePersistent(newEntry);          
          resp.sendRedirect("success.html");
          return;
      }
     }
    finally{

        System.out.println("Finally!");
    }

Answer 1

在您的情况下，请确保用户类每次都得到适当的增强，并建议您将用户类字段单独声明为持久字段。