Question

我正在从h2数据库中检索数据。我的问题是在q.setClass（）中。在这里，我尝试设置表chatUsers.class，数据库具有相同的类，但这表明没有表ChatUsers。那我该怎么办？

如果我不写q.setClass（）。那么它正在提供数据，但是有一个问题，那就是我无法获取该类的列表。

ChatUser类

import javax.jdo.JDOHelper;
import javax.jdo.PersistenceManager;
import javax.jdo.PersistenceManagerFactory;
import javax.jdo.Query;
import javax.jdo.annotations.IdGeneratorStrategy;
import javax.jdo.annotations.PersistenceCapable;
import javax.jdo.annotations.Persistent;
import javax.jdo.annotations.PrimaryKey;
import java.util.List;
import java.util.Properties;

@PersistenceCapable(detachable="true")
public class ChatUsers {

    @PrimaryKey
    @Persistent(valueStrategy = IdGeneratorStrategy.INCREMENT)
    int id;
    String user;
    String mobileNo;
    String email;
    String password;

    public ChatUsers(String user, String password, String mobileNo, String email) {
        this.user = user;
        this.mobileNo = mobileNo;
        this.email = email;
        this.password = password;
    }

    public String getPassword() {
        return password;
    }

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

    public int getId() {
        return id;
    }

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

    public String getUser() {
        return user;
    }

    public void setUser(String user) {
        this.user = user;
    }

    public String getMobileNo() {
        return mobileNo;
    }

    public void setMobileNo(String mobileNo) {
        this.mobileNo = mobileNo;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

检索逻辑

public static List<ChatUsers> getAllUsersList() {
        PersistenceManagerFactory pmf = JDOHelper.getPersistenceManagerFactory(setProperties());
        PersistenceManager pm = pmf.getPersistenceManager();
        List<ChatUsers> chatUsersList = null;
        pm.currentTransaction().begin();
        try {
            Query q = pm.newQuery("javax.jdo.query.SQL","SELECT * FROM `CHATUSERS`");
            q.setClass(ChatUsers.class);//This line has error
             chatUsersList = (List<ChatUsers>) q.execute();
        }catch (Exception ex)
        {
            System.out.println(ex);
        }

        return chatUsersList;
    }

错误代码

javax.jdo.JDOUserException: Persistent class "ChatUsers" has no table in the database, but the operation requires it. Please check the specification of the MetaData for this class.
NestedThrowables:
org.datanucleus.store.rdbms.exceptions.NoTableManagedException: Persistent class "ChatUsers" has no table in the database, but the operation requires it. Please check the specification of the MetaData for this class.

Answer 1

当执行execute（）查询时，应改用executeList（）。 [1]

另一个解决方案可能是使用setResultClass（）而不是setClass（）。 [1]

第一个解决方案的示例是：

    Query query = pm.newQuery("javax.jdo.query.SQL", "SELECT MY_ID, MY_NAME FROM MYTABLE");
query.setClass(MyClass.class);
List<MyClass> results = query.executeList();

[1]搜索“设置候选课程 ”和“定义结果类型 “”（位于文档URL：http://www.datanucleus.org/products/accessplatform/jdo/query.html

中）

javax.jdo.JDOUserException：持久类“ ChatUsers”在数据库中没有表

1 个答案: