Hibernate OnDelete Cascade not working for MySql but Works on postgres and Ms-Sql

Question

I'm having 2 Entities. Thread entity and Post entity using OnetoOne mapping from Post->Thread.

A Thread entity contains Numerous Posts. I know i should have used OnetoMany instead of OnetoOne, but for avoiding all the Collections problems i'm using OnetoOne

Now the problem is, when i delete a Thread, all the post associated with it must also be removed. I'm successful in doing it by using

@OnDelete(action = OnDeleteAction.CASCADE)

But it works only on Postgres and Ms-SQl but not on MySql(Tried InnoDb as well). The on delete cascade is not generated in the schema generation query.

Following are the code

//Thread Entity
@Id
@GeneratedValue
@Column(name = "thread_id")
private int ThreadID;

---

//Post Entity
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "post_id")
private int PostID;

@OneToOne()
@OnDelete(action = OnDeleteAction.CASCADE)
private thread ThreadID;

I get the following error While deleting an item from Thread entity using the following query

session.delete(session.load(thread.class,1));

Sep 02, 2014 8:33:51 PM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions WARN: SQL Error: 1451, SQLState: 23000 Sep 02, 2014 8:33:51 PM org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions ERROR: Cannot delete or update a parent row: a foreign key constraint fails (forum.post_tbl, CONSTRAINT FK_bfbv5nknqj7ppd5630scimhtb FOREIGN KEY (ThreadID_thread_id) REFERENCES thread_tbl (thread_id)) org.hibernate.exception.ConstraintViolationException: could not execute statement at org.hibernate.exception.internal.SQLExceptionTypeDelegate.convert(SQLExceptionTypeDelegate.java:74) at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49) at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:125) at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:110) at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:136) at org.hibernate.engine.jdbc.batch.internal.NonBatchingBatch.addToBatch(NonBatchingBatch.java:58) at org.hibernate.persister.entity.AbstractEntityPersister.delete(AbstractEntityPersister.java:3343) at org.hibernate.persister.entity.AbstractEntityPersister.delete(AbstractEntityPersister.java:3546) at org.hibernate.action.internal.EntityDeleteAction.execute(EntityDeleteAction.java:100) at org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:377) at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:369) at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:293) at org.hibernate.event.internal.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:339) at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:52) at org.hibernate.internal.SessionImpl.flush(SessionImpl.java:1234) at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:404) at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.beforeTransactionCommit(JdbcTransaction.java:101) at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.commit(AbstractTransactionImpl.java:175) at test.main(test.java:84) Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot delete or update a parent row: a foreign key constraint fails (forum.post_tbl, CONSTRAINT FK_bfbv5nknqj7ppd5630scimhtb FOREIGN KEY (ThreadID_thread_id) REFERENCES thread_tbl (thread_id)) HibernateException : could not execute statement at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:408) at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) at com.mysql.jdbc.Util.getInstance(Util.java:386) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1040) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4120) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4052) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2503) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2664) at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2794) at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2155) at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2458) at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2375) at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2359) at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:133) ... 14 more BUILD SUCCESSFUL (total time: 2 seconds)

Please help me find a way out of this.

Answer 1

This is what I did to resolve this problem based on Spring Boot.

Solution

from

// application.properties  
spring.jpa.database-platform=org.hibernate.dialect.MySQLDialect

to

spring.jpa.database-platform=org.hibernate.dialect.MySQL5InnoDBDialect

Explanation
As you can see below, it seems like the default value for CascadeDelete at MySQL5InnoDBDialect.java only support Cascade.

// MySQLDialect.java
@Override
    public boolean supportsCascadeDelete() {
        return false;
    }

// MySQL5InnoDBDialect.java
@Override
    public boolean supportsCascadeDelete() {
        return true;
    }