FAQs and Solutions for Java Frameworks

Java Framework FAQs and Solutions

1. How to choose the right Java framework?

• Spring Framework: Comprehensive and popular for building enterprise-level applications.
• Hibernate: ORM (Object Relational Mapping) framework that simplifies interaction with the database.
• Struts 2: MVC (Model-View-Controller) framework for building web applications.
• JUnit: Unit testing framework to ensure the correctness of the code.

2. How to solve Spring Bean injection problem?

• Check the bean definition for errors.
• Make sure the @Autowired annotation is applied correctly.
• Consider using the @Qualifier annotation to specify the name of the bean.

3. How to handle Hibernate lazy loading exception?

• Add the @Fetch annotation to the entity class to control lazy loading behavior.
• Use the initialize() method to explicitly initialize the associated object.
• Set the hibernate.enable_lazy_load_no_trans property to true.

4. How to solve Struts 2 interceptor problem?

• Check the interceptor configuration for errors.
• Make sure the interceptor class is implemented correctly.
• Use console mode to debug the interceptor (struts2-console-plugin).

5. How to improve the efficiency of JUnit unit testing?

• Use the @RepeatedTest annotation to run the test repeatedly.
• Use @ParameterizedTest annotation to pass parameters.
• Use the Mockito framework to mock dependencies.

Practical case: Building a CRUD (create, read, update, delete) application using Spring MVC and MySQL

@SpringBootApplication
public class CrudApp {
    public static void main(String[] args) {
        SpringApplication.run(CrudApp.class, args);
    }
}

@Entity
class Person {
    @Id
    @GeneratedValue
    private Long id;
    private String name;
    private int age;
}

@Repository
interface PersonRepository extends CrudRepository<Person, Long> {}

@RestController
class PersonController {
    @Autowired
    private PersonRepository personRepository;

    @GetMapping("/person")
    public List<Person> getAll() {
        return personRepository.findAll();
    }

    @PostMapping("/person")
    public Person create(@RequestBody Person person) {
        return personRepository.save(person);
    }

    @GetMapping("/person/{id}")
    public Person getById(@PathVariable Long id) {
        return personRepository.findById(id).orElse(null);
    }

    @PutMapping("/person/{id}")
    public Person update(@PathVariable Long id, @RequestBody Person person) {
        Person existing = personRepository.findById(id).orElse(null);
        if (existing != null) {
            existing.setName(person.getName());
            existing.setAge(person.getAge());
            return personRepository.save(existing);
        }
        return null;
    }

    @DeleteMapping("/person/{id}")
    public void delete(@PathVariable Long id) {
        personRepository.deleteById(id);
    }
}

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