Mapping 2 Tables with same structure in Hibernate

I have an existing application with an entity, for example Employee (Table EMP) and it is used at several places. Now after a long time, a replica (EMP_ARC) for the table EMP is created and we are supposed to refer it in certain scenarios.

As the table structure is exactly same I thought of reusing the POJO declaration. But I could not find a way to reuse the same POJO for two different table declarations. (I had seen examples of XML mapping to map one POJO to multiple tables but our application is using annotations and not able to find such option with annotation)

I cannot use Inheritance strategy because polymorphic queries will degrade the performance of the application and the EMP_ARC table has to be referred only when required.

Could anyone please tell me if creating a duplicate POJO and mapping it to the replica table is the only solution or any other approach is available.

**Sample Code:**



Table structure for EMP and EMP_ARC (exactly same structure)

EMP_ID LONG

EMP_NAME VARCHAR2(100)



**Existing Java Bean mapped to EMP**

**This entity bean cannot be modified**

//getter and setters omitted



@Entity

@Table(name="EMP")

public class Employee{



  @Id

  @Column(name="EMP_ID") 

  Long empid;



  @Column(name="EMP_NAME")

  String empName;

}



//Scenario 1 Query EMP table

String hql = "from Employee";



//Scenario 2 Query EMP_ARC table -- Like SELECT * FROM EMP_ARC

//Not sure of how to write the HQL using the same Employee POJO.

//Output of this HQL has to be an Employee POJO.

I want to map the same Employee POJO to the table EMP_ARC also but not able to find a way.

Alternatively, if I can selectively enable/disable polymorphic queries then I will be able to use Inheritance with strategy TABLE_PER_CLASS.

--- Workaround ---

To dynamically enable or disable polymorphic queries, I am using two different session factories.

I have two POJOs Employee and EmployeeArc (inheriting Employee).

Inheritance strategy used is TABLE_PER_CLASS.

One session factory will refer to the Employee entity alone and the other session factory will have both the Employee and EmployeeArc entities.

Whenever polymorphic query feature is not required then I will use the first session factory, otherwise use the second one.

If anybody is aware of a better solution, please help me in solving this in a better way.

edited Nov 28 '18 at 10:16

asked Nov 20 '18 at 10:15

Jayalakshmi Das

Have you produced any code? If so, please share it.

– Christopher
Nov 20 '18 at 10:22

Hi @Christopher, I have placed the sample code. Could you please help.

– Jayalakshmi Das
Nov 23 '18 at 8:34

add a comment |

I cannot use Inheritance strategy because polymorphic queries will degrade the performance of the application and the EMP_ARC table has to be referred only when required.

Could anyone please tell me if creating a duplicate POJO and mapping it to the replica table is the only solution or any other approach is available.

**Sample Code:**



Table structure for EMP and EMP_ARC (exactly same structure)

EMP_ID LONG

EMP_NAME VARCHAR2(100)



**Existing Java Bean mapped to EMP**

**This entity bean cannot be modified**

//getter and setters omitted



@Entity

@Table(name="EMP")

public class Employee{



  @Id

  @Column(name="EMP_ID") 

  Long empid;



  @Column(name="EMP_NAME")

  String empName;

}



//Scenario 1 Query EMP table

String hql = "from Employee";



//Scenario 2 Query EMP_ARC table -- Like SELECT * FROM EMP_ARC

//Not sure of how to write the HQL using the same Employee POJO.

//Output of this HQL has to be an Employee POJO.

I want to map the same Employee POJO to the table EMP_ARC also but not able to find a way.

Alternatively, if I can selectively enable/disable polymorphic queries then I will be able to use Inheritance with strategy TABLE_PER_CLASS.

--- Workaround ---

To dynamically enable or disable polymorphic queries, I am using two different session factories.

I have two POJOs Employee and EmployeeArc (inheriting Employee).

Inheritance strategy used is TABLE_PER_CLASS.

One session factory will refer to the Employee entity alone and the other session factory will have both the Employee and EmployeeArc entities.

Whenever polymorphic query feature is not required then I will use the first session factory, otherwise use the second one.

If anybody is aware of a better solution, please help me in solving this in a better way.

edited Nov 28 '18 at 10:16

asked Nov 20 '18 at 10:15

Jayalakshmi Das

Have you produced any code? If so, please share it.

– Christopher
Nov 20 '18 at 10:22

Hi @Christopher, I have placed the sample code. Could you please help.

– Jayalakshmi Das
Nov 23 '18 at 8:34

add a comment |

I cannot use Inheritance strategy because polymorphic queries will degrade the performance of the application and the EMP_ARC table has to be referred only when required.

Could anyone please tell me if creating a duplicate POJO and mapping it to the replica table is the only solution or any other approach is available.

**Sample Code:**



Table structure for EMP and EMP_ARC (exactly same structure)

EMP_ID LONG

EMP_NAME VARCHAR2(100)



**Existing Java Bean mapped to EMP**

**This entity bean cannot be modified**

//getter and setters omitted



@Entity

@Table(name="EMP")

public class Employee{



  @Id

  @Column(name="EMP_ID") 

  Long empid;



  @Column(name="EMP_NAME")

  String empName;

}



//Scenario 1 Query EMP table

String hql = "from Employee";



//Scenario 2 Query EMP_ARC table -- Like SELECT * FROM EMP_ARC

//Not sure of how to write the HQL using the same Employee POJO.

//Output of this HQL has to be an Employee POJO.

I want to map the same Employee POJO to the table EMP_ARC also but not able to find a way.

Alternatively, if I can selectively enable/disable polymorphic queries then I will be able to use Inheritance with strategy TABLE_PER_CLASS.

--- Workaround ---

To dynamically enable or disable polymorphic queries, I am using two different session factories.

I have two POJOs Employee and EmployeeArc (inheriting Employee).

Inheritance strategy used is TABLE_PER_CLASS.

One session factory will refer to the Employee entity alone and the other session factory will have both the Employee and EmployeeArc entities.

Whenever polymorphic query feature is not required then I will use the first session factory, otherwise use the second one.

If anybody is aware of a better solution, please help me in solving this in a better way.

edited Nov 28 '18 at 10:16

asked Nov 20 '18 at 10:15

Jayalakshmi Das

I cannot use Inheritance strategy because polymorphic queries will degrade the performance of the application and the EMP_ARC table has to be referred only when required.

Could anyone please tell me if creating a duplicate POJO and mapping it to the replica table is the only solution or any other approach is available.

**Sample Code:**



Table structure for EMP and EMP_ARC (exactly same structure)

EMP_ID LONG

EMP_NAME VARCHAR2(100)



**Existing Java Bean mapped to EMP**

**This entity bean cannot be modified**

//getter and setters omitted



@Entity

@Table(name="EMP")

public class Employee{



  @Id

  @Column(name="EMP_ID") 

  Long empid;



  @Column(name="EMP_NAME")

  String empName;

}



//Scenario 1 Query EMP table

String hql = "from Employee";



//Scenario 2 Query EMP_ARC table -- Like SELECT * FROM EMP_ARC

//Not sure of how to write the HQL using the same Employee POJO.

//Output of this HQL has to be an Employee POJO.

I want to map the same Employee POJO to the table EMP_ARC also but not able to find a way.

Alternatively, if I can selectively enable/disable polymorphic queries then I will be able to use Inheritance with strategy TABLE_PER_CLASS.

--- Workaround ---

To dynamically enable or disable polymorphic queries, I am using two different session factories.

I have two POJOs Employee and EmployeeArc (inheriting Employee).

Inheritance strategy used is TABLE_PER_CLASS.

One session factory will refer to the Employee entity alone and the other session factory will have both the Employee and EmployeeArc entities.

Whenever polymorphic query feature is not required then I will use the first session factory, otherwise use the second one.

If anybody is aware of a better solution, please help me in solving this in a better way.

hibernate-mapping

edited Nov 28 '18 at 10:16

asked Nov 20 '18 at 10:15

Jayalakshmi Das

edited Nov 28 '18 at 10:16

asked Nov 20 '18 at 10:15

Jayalakshmi Das

edited Nov 28 '18 at 10:16

asked Nov 20 '18 at 10:15

Jayalakshmi Das

asked Nov 20 '18 at 10:15

Jayalakshmi Das

asked Nov 20 '18 at 10:15

Jayalakshmi Das

Have you produced any code? If so, please share it.

– Christopher
Nov 20 '18 at 10:22

Hi @Christopher, I have placed the sample code. Could you please help.

– Jayalakshmi Das
Nov 23 '18 at 8:34

add a comment |

Have you produced any code? If so, please share it.

– Christopher
Nov 20 '18 at 10:22

Hi @Christopher, I have placed the sample code. Could you please help.

– Jayalakshmi Das
Nov 23 '18 at 8:34

Have you produced any code? If so, please share it.

– Christopher
Nov 20 '18 at 10:22

Hi @Christopher, I have placed the sample code. Could you please help.

– Jayalakshmi Das
Nov 23 '18 at 8:34

add a comment |

1 Answer
1

active

oldest

votes

You could go with inherited classes/entities. As I do not know your exact usecase, I would suggest you check these annotation-keywords:

@MappedSuperclass

@Inheritance

Here is an explanation about their differences: @MappedSuperclass vs. @Inheritance

answered Nov 23 '18 at 9:43

Tobi

2198

Not able to use this because I cannot modify the existing class to use MappedSuperClass and I don't want polymorphic queries to be enabled while using Inheritance. If there is a way to selectively disable polymorphic queries then I can use Inheritance

– Jayalakshmi Das
Nov 26 '18 at 13:39

Then I do not see a possibility do reuse the POJO. I think, you have to duplicate your POJO here :-(

– Tobi
Nov 26 '18 at 13:42

Thank you for confirming. If you are aware of programmatically disabling polymorphic queries or any workaround for dynamically enabling/disabling them, please let me know.

– Jayalakshmi Das
Nov 27 '18 at 6:52

add a comment |

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

You could go with inherited classes/entities. As I do not know your exact usecase, I would suggest you check these annotation-keywords:

@MappedSuperclass

@Inheritance

Here is an explanation about their differences: @MappedSuperclass vs. @Inheritance

answered Nov 23 '18 at 9:43

Tobi

2198

Not able to use this because I cannot modify the existing class to use MappedSuperClass and I don't want polymorphic queries to be enabled while using Inheritance. If there is a way to selectively disable polymorphic queries then I can use Inheritance

– Jayalakshmi Das
Nov 26 '18 at 13:39

Then I do not see a possibility do reuse the POJO. I think, you have to duplicate your POJO here :-(

– Tobi
Nov 26 '18 at 13:42

Thank you for confirming. If you are aware of programmatically disabling polymorphic queries or any workaround for dynamically enabling/disabling them, please let me know.

– Jayalakshmi Das
Nov 27 '18 at 6:52

add a comment |

You could go with inherited classes/entities. As I do not know your exact usecase, I would suggest you check these annotation-keywords:

@MappedSuperclass

@Inheritance

Here is an explanation about their differences: @MappedSuperclass vs. @Inheritance

answered Nov 23 '18 at 9:43

Tobi

2198

Not able to use this because I cannot modify the existing class to use MappedSuperClass and I don't want polymorphic queries to be enabled while using Inheritance. If there is a way to selectively disable polymorphic queries then I can use Inheritance

– Jayalakshmi Das
Nov 26 '18 at 13:39

Then I do not see a possibility do reuse the POJO. I think, you have to duplicate your POJO here :-(

– Tobi
Nov 26 '18 at 13:42

Thank you for confirming. If you are aware of programmatically disabling polymorphic queries or any workaround for dynamically enabling/disabling them, please let me know.

– Jayalakshmi Das
Nov 27 '18 at 6:52

add a comment |

You could go with inherited classes/entities. As I do not know your exact usecase, I would suggest you check these annotation-keywords:

@MappedSuperclass

@Inheritance

Here is an explanation about their differences: @MappedSuperclass vs. @Inheritance

answered Nov 23 '18 at 9:43

Tobi

2198

You could go with inherited classes/entities. As I do not know your exact usecase, I would suggest you check these annotation-keywords:

@MappedSuperclass

@Inheritance

Here is an explanation about their differences: @MappedSuperclass vs. @Inheritance

answered Nov 23 '18 at 9:43

Tobi

2198

answered Nov 23 '18 at 9:43

Tobi

2198

answered Nov 23 '18 at 9:43

Tobi

2198

answered Nov 23 '18 at 9:43

Tobi

2198

Not able to use this because I cannot modify the existing class to use MappedSuperClass and I don't want polymorphic queries to be enabled while using Inheritance. If there is a way to selectively disable polymorphic queries then I can use Inheritance

– Jayalakshmi Das
Nov 26 '18 at 13:39

Then I do not see a possibility do reuse the POJO. I think, you have to duplicate your POJO here :-(

– Tobi
Nov 26 '18 at 13:42

Thank you for confirming. If you are aware of programmatically disabling polymorphic queries or any workaround for dynamically enabling/disabling them, please let me know.

– Jayalakshmi Das
Nov 27 '18 at 6:52

add a comment |

Not able to use this because I cannot modify the existing class to use MappedSuperClass and I don't want polymorphic queries to be enabled while using Inheritance. If there is a way to selectively disable polymorphic queries then I can use Inheritance

– Jayalakshmi Das
Nov 26 '18 at 13:39

Then I do not see a possibility do reuse the POJO. I think, you have to duplicate your POJO here :-(

– Tobi
Nov 26 '18 at 13:42

Thank you for confirming. If you are aware of programmatically disabling polymorphic queries or any workaround for dynamically enabling/disabling them, please let me know.

– Jayalakshmi Das
Nov 27 '18 at 6:52

Not able to use this because I cannot modify the existing class to use MappedSuperClass and I don't want polymorphic queries to be enabled while using Inheritance. If there is a way to selectively disable polymorphic queries then I can use Inheritance

– Jayalakshmi Das
Nov 26 '18 at 13:39

Then I do not see a possibility do reuse the POJO. I think, you have to duplicate your POJO here :-(

– Tobi
Nov 26 '18 at 13:42

Thank you for confirming. If you are aware of programmatically disabling polymorphic queries or any workaround for dynamically enabling/disabling them, please let me know.

– Jayalakshmi Das
Nov 27 '18 at 6:52

add a comment |

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