如何構建一個JPA assossiation：人都有與其他人（朋友）

Question

我有有朋友一個實體的人，所以assosiation給其他人：

@Entity 
public class Person extends Model { 

    @Id 
    @Constraints.Required 
    @Formats.NonEmpty 
    public Long id; 

    @OneToMany 
    public List<Person> friends = new ArrayList<>(); 

如果我登錄的朋友attribut我看到這一點：BeanList deferred

如果我嘗試添加一個朋友是這樣的：

public void addFriend(Person person) { 
    this.contacts.add(person); 
    this.save("friends"); 
    this.update(); 

} 

我得到這個錯誤：

[error] Caused by: org.h2.jdbc.JdbcSQLException: Column "T1.PERSON_ID" not found; SQL statement: 
[error] select t0.id c0 
[error]   , t1.id c1, t1.first_name c2, t1.last_name c3, t1.gender c4, t1.self_description c5, t1.profile_image c6, t1.registration_date c7, t1.person_status c8, t1.second_mail c9, t1.user_code c10, t1.user_email c11, t1.work_place_id c12, t1.job_id c13, t1.life_cycle_stage_id c14, t1.role_id c15, t1.mentor_id c16 
[error] from person t0 
[error] left outer join person t1 on t1.person_id = t0.id 
[error] where t0.id = ? 
[error] order by t0.id [42122-168] 
[error]  at org.h2.message.DbException.getJdbcSQLException(DbException.java:329) 
[error]  at org.h2.message.DbException.get(DbException.java:169) 
[error]  at org.h2.message.DbException.get(DbException.java:146) 
[error]  at org.h2.expression.ExpressionColumn.optimize(ExpressionColumn.java:138) 
[error]  at org.h2.expression.Comparison.optimize(Comparison.java:159) 
[error]  at org.h2.command.dml.Select.setEvaluatableRecursive(Select.java:944) 
[error]  at org.h2.command.dml.Select.preparePlan(Select.java:923) 
[error]  at org.h2.command.dml.Select.prepare(Select.java:823) 
[error]  at org.h2.command.Parser.prepareCommand(Parser.java:218) 
[error]  at org.h2.engine.Session.prepareLocal(Session.java:415) 
[error]  at org.h2.engine.Session.prepareCommand(Session.java:364) 
[error]  at org.h2.jdbc.JdbcConnection.prepareCommand(JdbcConnection.java:1109) 
[error]  at org.h2.jdbc.JdbcPreparedStatement.<init>(JdbcPreparedStatement.java:74) 
[error]  at org.h2.jdbc.JdbcConnection.prepareStatement(JdbcConnection.java:264) 
[error]  at com.jolbox.bonecp.ConnectionHandle.prepareStatement(ConnectionHandle.java:820) 
[error]  at com.avaje.ebeaninternal.server.query.CQuery.prepareBindExecuteQuery(CQuery.java:365) 
[error]  at com.avaje.ebeaninternal.server.query.CQueryEngine.findMany(CQueryEngine.java:174) 
[error]  ... 44 more 

我也嘗試過多對多的關係。然後我得到這個：

[error] play - Duplicate column name "PERSON_ID"; SQL statement: 
create table person_person (
person_id      bigint not null, 
person_id      bigint not null, 
constraint pk_person_person primary key (person_id, person_id)) [42121-168] [ERROR:42121, SQLSTATE:42S21] 
[info] c.j.b.BoneCP - Shutting down connection pool... 
[info] c.j.b.BoneCP - Connection pool has been shutdown. 
[error] Test common.person.PersonModelTest.addContact failed: Database 'default' is in inconsistent state![An evolution has not been applied properly. Please check the problem and resolve it manually before marking it as resolved.] 
[error]  at play.api.db.evolutions.Evolutions$.checkEvolutionsState(Evolutions.scala:177) 
[error]  at play.api.db.evolutions.Evolutions$.applyScript(Evolutions.scala:275) 
[error]  at play.api.db.evolutions.EvolutionsPlugin$$anonfun$onStart$1$$anonfun$apply$1.apply$mcV$sp(Evolutions.scala:444) 
[error]  at play.api.db.evolutions.EvolutionsPlugin.withLock(Evolutions.scala:483) 
[error]  at play.api.db.evolutions.EvolutionsPlugin$$anonfun$onStart$1.apply(Evolutions.scala:439) 
[error]  at play.api.db.evolutions.EvolutionsPlugin$$anonfun$onStart$1.apply(Evolutions.scala:437) 
[error]  at scala.collection.immutable.List.foreach(List.scala:309) 
[error]  at play.api.db.evolutions.EvolutionsPlugin.onStart(Evolutions.scala:437) 
[error]  at play.api.Play$$anonfun$start$1$$anonfun$apply$mcV$sp$1.apply(Play.scala:63) 
[error]  at play.api.Play$$anonfun$start$1$$anonfun$apply$mcV$sp$1.apply(Play.scala:63) 
[error]  at scala.collection.immutable.List.foreach(List.scala:309) 
[error]  at play.api.Play$$anonfun$start$1.apply$mcV$sp(Play.scala:63) 
[error]  at play.api.Play$$anonfun$start$1.apply(Play.scala:63) 
[error]  at play.api.Play$$anonfun$start$1.apply(Play.scala:63) 
[error]  at play.utils.Threads$.withContextClassLoader(Threads.scala:18) 
[error]  at play.api.Play$.start(Play.scala:62) 
[error]  at play.api.Play.start(Play.scala) 
[error]  at play.test.Helpers.start(Helpers.java:354) 
[error]  at common.CommonTest.setUp(CommonTest.java:20) 
[error]  ... 

任何想法？

Answer 1

我找到答案here由於chssply76

Answer 2

你可以嘗試這樣的事情嗎？

@ManyToOne(mappedBy="friends") 
@OneToMany 
public List<Person> friends = new ArrayList<>();