4

我想构建一个应用程序，其中由电子邮件地址标识的用户可以拥有多个应用程序帐户。每个帐户可以有一个或多个用户。我正在尝试将 JDO 存储功能与 Google App Engine Java 一起使用。这是我的尝试：

@PersistenceCapable
@Inheritance(strategy = InheritanceStrategy.NEW_TABLE)
public class AppAccount {
     @PrimaryKey
     @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
     private Long id;

    @Persistent
    private String companyName;

    @Persistent
    List<Invoices> invoices = new ArrayList<Invoices>();

    @Persistent
    List<AppUser> users = new ArrayList<AppUser>();

    // Getter Setters and Other Fields
}

@PersistenceCapable
@EmbeddedOnly
public class AppUser {

    @Persistent
    private String username;

    @Persistent
    private String firstName;

    @Persistent
    private String lastName;

     // Getter Setters and Other Fields
}

当用户登录时，我想检查他属于多少个帐户。如果他或她属于多个，那么他或她将看到一个仪表板，他/她可以在其中单击他/她想要加载的帐户。这是我检索他/她注册的应用帐户列表的代码。

public static List<AppAccount> getUserAppAccounts(String username) {
    PersistenceManager pm = JdoUtil.getPm();
    Query q = pm.newQuery(AppAccount.class);
    q.setFilter("users.username == usernameParam");
    q.declareParameters("String usernameParam");
    return (List<AppAccount>) q.execute(username);
}

但我得到下一个错误：

SELECT FROM invoices.server.AppAccount WHERE users.username == usernameParam PARAMETERS String usernameParam: Encountered a variable expression that isn't part of a join.  Maybe you're referencing a non-existent field of an embedded class.
org.datanucleus.store.appengine.FatalNucleusUserException: SELECT FROM com.softamo.pelicamo.invoices.server.AppAccount WHERE users.username == usernameParam PARAMETERS String usernameParam: Encountered a variable expression that isn't part of a join.  Maybe you're referencing a non-existent field of an embedded class.
    at org.datanucleus.store.appengine.query.DatastoreQuery.getJoinClassMetaData(DatastoreQuery.java:1154)
    at org.datanucleus.store.appengine.query.DatastoreQuery.addLeftPrimaryExpression(DatastoreQuery.java:1066)
    at org.datanucleus.store.appengine.query.DatastoreQuery.addExpression(DatastoreQuery.java:846)
    at org.datanucleus.store.appengine.query.DatastoreQuery.addFilters(DatastoreQuery.java:807)
    at org.datanucleus.store.appengine.query.DatastoreQuery.performExecute(DatastoreQuery.java:226)
    at org.datanucleus.store.appengine.query.JDOQLQuery.performExecute(JDOQLQuery.java:85)
    at org.datanucleus.store.query.Query.executeQuery(Query.java:1489)
    at org.datanucleus.store.query.Query.executeWithArray(Query.java:1371)
    at org.datanucleus.jdo.JDOQuery.execute(JDOQuery.java:243)
    at com.softamo.pelicamo.invoices.server.Store.getUserAppAccounts(Store.java:82)
    at com.softamo.pelicamo.invoices.test.server.StoreTest.testgetUserAppAccounts(StoreTest.java:39)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:31)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:76)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:46)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

有任何想法吗？

我是否完全错误地理解了 JDO 持久性？

4

1 回答 1

5

该类AppAccount有一个users变量，即 a List。List没有直接的用户名属性。

你需要做这样的事情：

@PersistenceCapable
@EmbeddedOnly
public class AppUser {

    @Persistent
    private String username;

    @Persistent
    private String firstName;

    @Persistent
    private String lastName;

    //override equals method for List .contains
    @Override
    public boolean equals(AppUser au) {
        return au.getUsername().equals(this.username);
    } 

     // Getter Setters and Other Fields
}

Query q = pm.newQuery(AppAccount.class);
//the : denotes an implicit variable will be passed to query execute method
q.setFilter("users.contains(:username)");
//create a new AppUser with the username you want to check, this query will find the AppAccount with any AppUser with the same username, because the .equals method of AppUser has been overridden to return true based on the username member variable
List<AppAccount> results = (List<AppAccount>)query.execute(new AppUser(username));
于 2010-04-04T23:18:51.353 回答