java – Persistance JDO – 如何使用JDOQL查询集合的属性？
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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.每个帐户可以包含一个或多个用户.我正在尝试将JDO存储功能与Google App Engine Java结合使用.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,我想检查他所属的帐户数量.如果他或她属于多个人,那么他或她将被提供一个仪表板,他/她可以点击他/她想要加载的帐户.这是我的代码,用于检索他/她注册的应用帐户列表.
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);
}
但我得到了下一个错误：
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？
我对JDO持久性完全错了吗？
解决方法:
AppAccount类具有一个List变量的用户变量. 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));
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