Managing transactions of dynamically created objects in spring - spring

Question

I have a web service which receives a data object(Let's call the class Student). At the web service, I wrap it using a StudentWrapper object as follows
new StudentWrapper(student)
and I want the StudentWrapper class to have methods such as save which would save the data to the database. I want to use the spring framework to annotate the save method so that it will run within a transaction. But then the StudendWrapper object would have to be a spring bean(defined in XML). If it is a spring bean, then I won't be instantiating it as I have shown above.
My question is how can I make the StudentWrapper a Spring bean (so that I can use Spring annotations to manage the transactions) but pass the Student object (that I receive over the web service) in to the StudentWrapper?
If there are any other suggestions that would help me in solving this problem, please share them as well.

Answer 1

If you really want to create the object using a constructor, make the StudentWrapper #Configurable and read up about using AspectJ to create prototype bean definitions for domain objects (section 9.8 of the reference manual.)
A simpler alternative, if you don't want to go with AspectJ but don't want a direct dependency on Spring is to encapsulate the prototype bean creation in a factory. I'll show you using JavaConfig, though you can do something similar in XML.
First the student object...
package internal;
public class Student {
private String name;
public Student(String name) {
this.name = name;
}
public String getName() {
return name;
}
#Override
public String toString() {
return "Student{name='" + name + "'}";
}
}
And now the wrapper object...
package internal;
public class StudentWrapper {
private Student student;
public StudentWrapper(Student student) {
this.student = student;
}
public Student getStudent() {
return student;
}
#Override
public String toString() {
return "StudentWrapper{student='" + student + "'} " + super.toString();
}
}
And now the factory,
package internal;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Component;
#Component
public class StudentWrapperFactory {
#Autowired
private ApplicationContext applicationContext;
public StudentWrapper newStudentWrapper(Student student) {
return (StudentWrapper) this.applicationContext.getBean("studentWrapper", student);
}
}
And now the JavaConfig, equivalent to an XML configuration
package internal;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Scope;
#Configuration
#ComponentScan(basePackages = "internal")
public class FooConfig {
#Bean
#Scope("prototype")
public StudentWrapper studentWrapper(Student student) {
return new StudentWrapper(student);
}
}
Finally the unit test...
package internal;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
#RunWith(SpringJUnit4ClassRunner.class)
#ContextConfiguration(classes = {FooConfig.class})
public class FooIntegrationTest {
#Autowired
private StudentWrapperFactory studentWrapperFactory;
#Test
public void foo() {
Student student1 = new Student("student 1");
Student student2 = new Student("student 2");
StudentWrapper bean1 = this.studentWrapperFactory.newStudentWrapper(student1);
StudentWrapper bean2 = this.studentWrapperFactory.newStudentWrapper(student2);
System.out.println(bean1);
System.out.println(bean2);
}
}
produces
StudentWrapper{student='Student{name='student 1'}'} internal.StudentWrapper#1b0fa7ff
StudentWrapper{student='Student{name='student 2'}'} internal.StudentWrapper#20de643a
As you can see from the object references of StudentWrapper, they're different prototype beans. #Transactional methods should work as expected in StudentWrapper.