Java – Help I have problem with select query in JPA

javajpa

i have problem i want to

select name_magazine from magazine

and i already import all library needed

and

Query q = EntityManger.createQuery ("SELECT name_magazine FROM Magazine");

List results = (List) q.getResultList ();

For(Sting s : result)

System.out.println(s);

but when i run this code it's error. can someone help me? Thx

this the error when i run the program

Exception in thread "AWT-EventQueue-0"
java.lang.Error:
java.lang.reflect.InvocationTargetException
at org.jdesktop.application.ApplicationAction.actionFailed(ApplicationAction.java:859)
at org.jdesktop.application.ApplicationAction.noProxyActionPerformed(ApplicationAction.java:665)
at org.jdesktop.application.ApplicationAction.actionPerformed(ApplicationAction.java:698)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
at javax.swing.AbstractButton.doClick(AbstractButton.java:357)
at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:1220)
at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:1261)
at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:272)
at java.awt.Component.processMouseEvent(Component.java:6041)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
at java.awt.Component.processEvent(Component.java:5806)
at java.awt.Container.processEvent(Container.java:2058)
at java.awt.Component.dispatchEventImpl(Component.java:4413)
at java.awt.Container.dispatchEventImpl(Container.java:2116)
at java.awt.Component.dispatchEvent(Component.java:4243)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4322)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3986)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3916)
at java.awt.Container.dispatchEventImpl(Container.java:2102)
at java.awt.Window.dispatchEventImpl(Window.java:2440)
at java.awt.Component.dispatchEvent(Component.java:4243)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)
Caused by:
java.lang.reflect.InvocationTargetException
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.jdesktop.application.ApplicationAction.noProxyActionPerformed(ApplicationAction.java:662)
… 29 more Caused by: java.lang.IllegalArgumentException: An
exception occured while creating a
query in EntityManager
at oracle.toplink.essentials.internal.ejb.cmp3.EntityManagerImpl.createQuery(EntityManagerImpl.java:209)
at tugas_rpl.Tugas_RPLView.Iseng(Tugas_RPLView.java:734)
… 34 more Caused by: Exception [TOPLINK-8034] (Oracle
TopLink Essentials – 2.0.1 (Build
b09d-fcs (12/06/2007))):
oracle.toplink.essentials.exceptions.EJBQLException
Exception Description: Error compiling
the query [Select m.Name from
magazine m]. Unknown abstract schema type
[magazine].
at oracle.toplink.essentials.exceptions.EJBQLException.unknownAbstractSchemaType(EJBQLException.java:494)
at oracle.toplink.essentials.internal.parsing.ParseTreeContext.classForSchemaName(ParseTreeContext.java:163)
at oracle.toplink.essentials.internal.parsing.VariableNode.resolveClass(VariableNode.java:280)
at oracle.toplink.essentials.internal.parsing.DotNode.resolveMapping(DotNode.java:254)
at oracle.toplink.essentials.internal.parsing.DotNode.endsWithDirectToField(DotNode.java:213)
at oracle.toplink.essentials.internal.parsing.SelectNode.selectingDirectToField(SelectNode.java:440)
at oracle.toplink.essentials.internal.parsing.SelectNode.hasOneToOneSelected(SelectNode.java:265)
at oracle.toplink.essentials.internal.parsing.SelectNode.hasOneToOneSelected(SelectNode.java:222)
at oracle.toplink.essentials.internal.parsing.SelectGenerationContext.computeUseParallelExpressions(SelectGenerationContext.java:105)
at oracle.toplink.essentials.internal.parsing.SelectGenerationContext.(SelectGenerationContext.java:88)
at oracle.toplink.essentials.internal.parsing.ParseTree.buildContextForReadQuery(ParseTree.java:382)
at oracle.toplink.essentials.internal.parsing.ParseTree.buildContext(ParseTree.java:370)
at oracle.toplink.essentials.internal.parsing.EJBQLParseTree.buildContext(EJBQLParseTree.java:68)
at oracle.toplink.essentials.internal.parsing.EJBQLParseTree.populateQuery(EJBQLParseTree.java:107)
at oracle.toplink.essentials.internal.ejb.cmp3.base.EJBQueryImpl.buildEJBQLDatabaseQuery(EJBQueryImpl.java:219)
at oracle.toplink.essentials.internal.ejb.cmp3.base.EJBQueryImpl.buildEJBQLDatabaseQuery(EJBQueryImpl.java:189)
at oracle.toplink.essentials.internal.ejb.cmp3.base.EJBQueryImpl.buildEJBQLDatabaseQuery(EJBQueryImpl.java:153)
at oracle.toplink.essentials.internal.ejb.cmp3.base.EJBQueryImpl.(EJBQueryImpl.java:114)
at oracle.toplink.essentials.internal.ejb.cmp3.base.EJBQueryImpl.(EJBQueryImpl.java:99)
at oracle.toplink.essentials.internal.ejb.cmp3.EJBQueryImpl.(EJBQueryImpl.java:86)
at oracle.toplink.essentials.internal.ejb.cmp3.EntityManagerImpl.createQuery(EntityManagerImpl.java:204)
… 35 more

I already try Vincent Ramdhanie,Guðmundur Bjarni suggestion

Query q = entityManager.createQuery("Select m.name from magazine m");

List result = (List) q.getResultList();

For(Sting s : result)

System.out.print(s);

but still error

this what library & variable i use

private javax.persistence.EntityManager entityManager;

import org.jdesktop.application.Action;

import org.jdesktop.application.ResourceMap;

import org.jdesktop.application.SingleFrameApplication;

import org.jdesktop.application.FrameView;

import org.jdesktop.application.TaskMonitor;

import org.jdesktop.application.Task;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.util.ArrayList;

import java.util.List;

import javax.swing.Timer;

import javax.swing.Icon;

import javax.swing.JDialog;

import javax.swing.JFrame;

import javax.swing.event.ListSelectionEvent;

import javax.swing.event.ListSelectionListener;

import org.jdesktop.beansbinding.AbstractBindingListener;

import org.jdesktop.beansbinding.Binding;

import org.jdesktop.beansbinding.PropertyStateEvent;

import javax.persistence.*;

Best Answer

You probably should say what the error is exactly.

However, assuming that you have an entity Magazine then the query should be:

 select m from Magazine m

If you want all magazines.

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Java – NoClassDefFoundError: javax/swing/GroupLayout$Group on Mac Computer

Under OS X the default version of Java is Java 1.5.

The only good Way to ensure the right jvm is with java Web start.

Java – Why I have NullPointerException here

Instead of hunting the root cause in the dark, I think it's better to explain how and why NPE's are caused and how they can be avoided, so that the OP can apply the newly gained knowledge to hunt his/her own trivial problem.

Look, object references (the variables) can contain either a fullworthy Object or simply nothing, which is null.

SomeObject someObject1 = new SomeObject(); // References something.
SomeObject someObject2 = null; // References nothing.

Now, if you're trying to access nothing (null), then you will undoubtely get a NullPointerException, simply because null doesn't have any variables or methods.

someObject1.doSomething(); // Works fine.
someObject2.doSomething(); // Throws NullPointerException.

Workarounding this is fairly simple. It can be done in basically two ways: either by instantiating it or just by ignoring it.

if (someObject2 == null) {
    someObject2 = new SomeObject();
}
someObject2.doSomething(); // No NPE anymore!

if (someObject2 != null) {
    someObject2.doSomething(); // No NPE anymore!
}

In case of a NPE, the first line number of the stacktrace points the exact line where the it is been caused. You told literally "line 272 is admin.birthList.add(list1);". This line contains two places where object references are been accessed/invoked (using the dot . operator). The first being admin.birthList and the second being birthList.add(list1). It's up to you to find out if one or both caused the NPE. If it is the first invocation, then admin is simply null. If it is the second invocation, then birthList is simply null. You can fix it by instantiating it with a fullworthy object.

Edit: If you have a hard time in determining the root cause (as turns out from comments), then you need to learn debugging. Run a debugger or just do "poor man's debugging" with help of a System.out.println() of every variable before accessing/invoking them. First look at line where the NPE is caused. If this is for example

admin.birthList.add(list1);

then you need to change it as follows to nail down the root cause:

System.out.println("admin: " + admin);
List<Birth> birthList = admin.birthList;
System.out.println("birthList: " + birthList);
birthList.add(list1);

check if any of them prints null. Alternatively you can also do:

if (admin == null) throw new NullPointerException("admin is null!");
List<Birth> birthList = admin.birthList;
if (birthList == null) throw new NullPointerException("birthList is null!");
birthList.add(list1);

you can also separate the individual invocations over separate lines so that you have enough to the line number to know which reference is null.

List<Birth> birthList = admin.birthList; // If NPE line points here, then admin is null.
birthList.add(list1); // If NPE line points here, then birthList is null.

Best Answer

Related Solutions

Java – NoClassDefFoundError: javax/swing/GroupLayout$Group on Mac Computer

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