Hibernate - No primary key Table

In Hibernate mapping, It is not possible to create a table without a primary key. If you are using annotations, you definitely need to use @Id in your class. But what happens if there is no primary key in your database table.

There is a workaround for this if your table is having some sort of unique relationship to any other table.

Consider two classes. Parent and a Child.

Parent has a primary key property but Child do not.

@Entity

@Table(name = "ParentTableName")

class Parent{

protected Integer id;

@Id

@Column(name = "PrimaryKeyColumnName", nullable = false)

public Integer getId() {

return id;

}

}

@Entity

@Table(name = "ChildTableName")

class Child{

private Parent parent;

@Id

@OneToOne @JoinColumn(name = "FKColumnNameInChildTable", nullable = false)

public Parent getParent() { return parent; }

public void setParent(Parent parent) { this.parent = parent;

}

}

Here even though, no primary key is specified in the database table, we are informing Hibernate to treat the Foreign Key as the primary key.

But what if you we have a unique relation on multiple columns in the child table?

In that case we can specify @Id annotation to all the relations and specify those relations with @Embeddable annotation.

Eclipse - Eclipse is running in a JRE, but a JDK is required

Eclipse by default runs on a JRE. But, there may be times you want a full JDK to run it. One example is using Maven Plug-in.

Change the eclipse.ini (Located in the same folder as in your eclipse.exe file) file with a vm argument pointing to your jdk.

The important things are :

1. Enter a new argument "vm" pointing to the java jdk's javaw.exe file

-vm

C:/Program Files/Java/jdk1.6.0_20/bin/javaw.exe

2. vm and the path should be in a separate line. So if you have

-vm C:/Program Files/Java/jdk1.6.0_20/bin/javaw.exe

in a single line, Eclipse can not identify it.

3. "vm" argument should be before "-vmargs" and after" --launcher.XXMaxPermSize"

-vm

C:/Program Files/Java/jdk1.6.0_20/bin/javaw.exe

-vmargs

-Dosgi.requiredJavaVersion=1.5

-Xms40m

-Xmx768m

-XX:MaxPermSize=256m

You can point to the java/bin folder also, for the vm argument. Some people got an exception because of a space in the file path location of java, so you might try installing Java into a non-space file path like C:/Java/jdk1.6.0_20.

Also you can see the thread in http://www.coderanch.com/t/488574/vc/Eclipse-running-JRE-but-JDK.

This also works the same way for the Spring Source Tool Suite and you can see this concerned thread, http://forum.springsource.org/showthread.php?t=86906.

Not Writable or Invalid Setter Method Exception :

org.springframework.beans.NotWritablePropertyException: Invalid property 'xxxxxx' of bean class [com.company.springhibernateintegration.classes.AddressDAOImpl]: Bean property 'hibernateTemplate' is not writable or has an invalid setter method. Does the parameter type of the setter match the return type of the getter?

Two reasons for occuring this exception is :

1. When the property is not specified in the bean and is mentioned in the bean registration in the application-context.xml
2. When you are trying to insert the 'xxxxx' property into the bean through a STATIC Setter.