使用 play 和 ebean 进行多对多查询答案

【问题标题】：ManyToMany query using play and ebean使用 play 和 ebean 进行多对多查询
【发布时间】：2014-03-01 20:35:30
【问题描述】：

我正在尝试使用具有多对多关系的查找器进行查询，但无法弄清楚这一点。使用 play 2.1.2 和 ebean 3.1.1（与 Play 打包）。

我有一个包含 MyContacts 和 MyContactGroups 的 MyUser 类。 MyContactGroups 与 MyContact 有一个多对多。我正在尝试编写一个查询，我可以在其中获取 MyUser 的 MyContactGroup 中的所有 MyContacts。下面查询失败的方法是findByContactGroupAndUser。

实体是：

@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);
}

测试：

@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);
}

例外：

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)

【问题讨论】：

标签： playframework-2.0 ebean

【解决方案1】：

我认为这基本上是因为我没有将 mappedBy 放在正确的实体上，并且可能将 Ebean 直接字段访问与 setter/getter 访问混合在一起。在 play 中，他们说您应该只使用 setter/getter 访问，因为 play 和 Ebean 代码增强之间存在一些冲突。以下直接与 Ebean 一起工作，我也能够让它在游戏中工作。

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;
    }
}

测试：

    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());
}

【讨论】：