问题
I'm trying to query using a finder with a ManyToMany relationship and have not been able to figure this out. Using play 2.1.2 and ebean 3.1.1 (packaged with Play).
I have a MyUser class that has MyContacts, and MyContactGroups. MyContactGroups has a ManyToMany with MyContact. I'm trying to write a query where I can get all the MyContacts that are in a MyContactGroup for a MyUser. The query method below that fails is findByContactGroupAndUser.
entities are:
@Entity
@Table(name = "my_user")
public class MyUser extends Model {
@Id
public Long id;
public String name;
@OneToMany(cascade = CascadeType.ALL)
public List<MyContact> myContacts = new ArrayList<MyContact>();
@OneToMany(cascade = CascadeType.ALL)
public List<MyContactGroup> myContactGroups = new ArrayList<MyContactGroup>();
public void addContact(MyContact myContact) {
myContacts.add(myContact);
}
public void addContactGroup(MyContactGroup myContactGroup) {
myContactGroups.add(myContactGroup);
}
public static Model.Finder<Long, MyUser> find = new Model.Finder<Long, MyUser>(
Long.class, MyUser.class);
}
@Entity
@Table(name = "my_contact")
public class MyContact extends Model {
@Id
public Long id;
public String name;
@ManyToOne
public MyUser myUser;
@ManyToMany(mappedBy = "myContacts")
public MyContactGroup myContactGroup;
public static Model.Finder<Long, MyContact> find = new Model.Finder<Long, MyContact>(
Long.class, MyContact.class);
public static Page<MyContact> findByContactGroupAndUser(MyUser myUser, MyContactGroup myContactGroup, int pageSize, int page) {
return find.where(Expr.and(Expr.eq("myContactGroup", myContactGroup),
Expr.eq("myUser", myUser)))
.findPagingList(pageSize).setFetchAhead(false).getPage(page);
}
}
@Entity
@Table(name = "my_contact_group")
public class MyContactGroup extends Model {
@Id
public Long id;
public String name;
@ManyToOne(cascade = CascadeType.ALL)
public MyUser myUser;
@ManyToMany(cascade = CascadeType.ALL)
public List<MyContact> myContacts = new ArrayList<MyContact>();
public void addContact(MyContact myContact) {
myContacts.add(myContact);
}
public static Model.Finder<Long, MyContactGroup> find = new Model.Finder<Long, MyContactGroup>(
Long.class, MyContactGroup.class);
}
The test:
@Test
public void testMyContactGroup() {
MyUser myUser = new MyUser();
myUser.name = "UserSteve";
myUser.save();
MyContact myContact = new MyContact();
myContact.name = "ContactBob";
myContact.myUser = myUser;
myUser.addContact(myContact);
myUser.save();
assertThat(MyUser.find.where().eq("name", "UserSteve").findUnique().name.equals("UserSteve"));
assertThat(myUser.myContacts.get(0).name.equals("ContactBob"));
MyContactGroup myContactGroup = new MyContactGroup();
myContactGroup.name = "myContactGroup";
myContactGroup.myUser = myUser;
myUser.addContactGroup(myContactGroup);
myUser.update();
assertThat(myUser.myContactGroups.get(0).name.equals("myContactGroup"));
myContactGroup = myUser.myContactGroups.get(0);
myContactGroup.addContact(myContact);
myUser.update();
Ebean.saveManyToManyAssociations(myContactGroup, "myContacts");
myUser = MyUser.find.where().eq("name", "UserSteve").findUnique();
assertThat(myUser.myContactGroups.get(0).name.equals("myContactGroup"));
assertThat(myUser.myContactGroups.get(0).myContacts.get(0).name.equals("ContactBob"));
myUser = MyUser.find.where().eq("name", "UserSteve").findUnique();
myContactGroup = myUser.myContactGroups.get(0);
assertThat(myContactGroup.name.equals("myContactGroup"));
assertThat(myUser.myContactGroups.get(0).myContacts.get(0).name.equals("ContactBob"));
log.info("doing lookup");
Page<MyContact> page = MyContact.findByContactGroupAndUser(myUser, myContactGroup, 10, 0);
assertThat(page.getList().size() == 1);
}
The exception:
javax.persistence.PersistenceException: java.util.concurrent.ExecutionException: java.lang.NullPointerException
at com.avaje.ebeaninternal.server.query.LimitOffsetPage.getList(LimitOffsetPage.java:64)
at ApplicationTest.testMyContactGroup(ApplicationTest.java:152)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:74)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:202)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:65)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)
Caused by: java.util.concurrent.ExecutionException: java.lang.NullPointerException
at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:252)
at java.util.concurrent.FutureTask.get(FutureTask.java:111)
at com.avaje.ebeaninternal.server.query.BaseFuture.get(BaseFuture.java:29)
at com.avaje.ebeaninternal.server.query.LimitOffsetPage.getList(LimitOffsetPage.java:62)
... 29 more
Caused by: java.lang.NullPointerException
at com.avaje.ebeaninternal.server.deploy.BeanPropertyAssocOne.getAssocOneIdValues(BeanPropertyAssocOne.java:411)
at com.avaje.ebeaninternal.server.expression.SimpleExpression.addBindValues(SimpleExpression.java:50)
at com.avaje.ebeaninternal.server.expression.LogicExpression.addBindValues(LogicExpression.java:56)
at com.avaje.ebeaninternal.util.DefaultExpressionList.buildBindValues(DefaultExpressionList.java:277)
at com.avaje.ebeaninternal.server.query.CQueryPredicates.prepare(CQueryPredicates.java:281)
at com.avaje.ebeaninternal.server.query.CQueryPredicates.prepare(CQueryPredicates.java:263)
at com.avaje.ebeaninternal.server.query.CQueryBuilder.buildQuery(CQueryBuilder.java:200)
at com.avaje.ebeaninternal.server.query.CQueryEngine.findMany(CQueryEngine.java:162)
at com.avaje.ebeaninternal.server.query.DefaultOrmQueryEngine.findMany(DefaultOrmQueryEngine.java:77)
at com.avaje.ebeaninternal.server.core.OrmQueryRequest.findList(OrmQueryRequest.java:272)
at com.avaje.ebeaninternal.server.core.DefaultServer.findList(DefaultServer.java:1502)
at com.avaje.ebeaninternal.server.query.CallableQueryList.call(CallableQueryList.java:26)
at com.avaje.ebeaninternal.server.query.CallableQueryList.call(CallableQueryList.java:15)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
at java.util.concurrent.FutureTask.run(FutureTask.java:166)
at com.avaje.ebeaninternal.server.lib.thread.PooledThread.doTheWork(PooledThread.java:89)
at com.avaje.ebeaninternal.server.lib.thread.PooledThread.run(PooledThread.java:62)
at java.lang.Thread.run(Thread.java:722)
回答1:
I think this was basically because I had not put mappedBy on the correct Entity, and possibly mixing Ebean direct field access with setter/getter access. In play they say you should only use setter/getter access, due to some conflicts between play and Ebean code enhancement. The following works with Ebean directly, and I was able to get it to work in play as well.
package app.data;
import com.avaje.ebean.validation.Length;
import javax.persistence.*;
import java.util.ArrayList;
import java.util.List;
/**
* Created by aakture on 3/2/14.
*/
@Entity
@Table(name="o_user")
public class User {
@Id
Integer id;
@Length(max = 20)
String name;
@OneToMany(cascade = CascadeType.ALL)
List<ContactGroup> contactGroups = new ArrayList<ContactGroup>();
@OneToMany(cascade = CascadeType.ALL)
List<Contact> contacts = new ArrayList<Contact>();
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List<ContactGroup> getContactGroups() {
return contactGroups;
}
public void setContactGroups(List<ContactGroup> contactGroups) {
this.contactGroups = contactGroups;
}
public List<Contact> getContacts() {
return contacts;
}
public void setContacts(List<Contact> contacts) {
this.contacts = contacts;
}
@Override
public String toString() {
return com.google.common.base.Objects.toStringHelper(this)
.add("id", id)
.add("name", name)
.add("contactGroups", contactGroups)
.toString();
}
}
package app.data;
import javax.persistence.*;
import java.util.ArrayList;
import java.util.List;
/**
* Created by aakture on 3/2/14.
*/
@Entity
@Table(name="o_contact")
public class Contact {
@Id
Integer id;
String name;
@ManyToOne
User user;
@ManyToMany
List<ContactGroup> contactGroups = new ArrayList<ContactGroup>();
public List<ContactGroup> getContactGroups() {
return contactGroups;
}
public void setContactGroups(List<ContactGroup> contactGroups) {
this.contactGroups = contactGroups;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
}
package app.data;
import javax.persistence.*;
import java.util.ArrayList;
import java.util.List;
/**
* Created by aakture on 3/2/14.
*/
@Entity
@Table(name="o_contact_group")
public class ContactGroup {
@Id
Integer id;
@ManyToOne
User user;
String name;
@ManyToMany(cascade = CascadeType.MERGE, mappedBy = "contactGroups")
List<Contact> contacts = new ArrayList<Contact>();
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
public List<Contact> getContacts() {
return contacts;
}
public void setContacts(List<Contact> contacts) {
this.contacts = contacts;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
Test:
public void test() {
User user = new User();
user.setName("UserBob");
Ebean.save(user);
ContactGroup contactGroup = new ContactGroup();
contactGroup.setName("Friends");
List<ContactGroup> contactGroupList = new ArrayList<ContactGroup>();
contactGroupList.add(contactGroup);
user.setContactGroups(contactGroupList);
Ebean.update(user);
user = Ebean.find(User.class).where().eq("name", "UserBob").findUnique();
List<ContactGroup> contactGroups = user.getContactGroups();
for(ContactGroup cg : contactGroups) {
System.out.println("contactGroup: " + cg.getName());
}
Contact contact = new Contact();
contact.setName("ContactSteve");
user.getContacts().add(contact);
Ebean.update(user);
user = Ebean.find(User.class).where().eq("name", "UserBob").findUnique();
for(Contact c : user.getContacts()) {
System.out.println("contact: " + c.getName());
}
Contact contactSteve = user.getContacts().get(0);
ContactGroup friends = user.getContactGroups().get(0);
friends.getContacts().add(contactSteve);
Ebean.saveManyToManyAssociations(friends, "contacts");
Ebean.update(user);
user = Ebean.find(User.class).where().eq("name", "UserBob").findUnique();
friends = user.getContactGroups().get(0);
List<Contact> contacts = friends.getContacts();
for (Contact c : contacts) {
System.out.println("contact: " + c.getName());
}
contact = Ebean.find(Contact.class).where().and(Expr.eq("user.name", "UserBob"), Expr.eq("contactGroups.name", "Friends")).findUnique();
System.out.println("contact: " + contact.getName());
}
来源：https://stackoverflow.com/questions/22120020/manytomany-query-using-play-and-ebean