Spring Data JPA (1)--repository and Crudrepository interfaces

The recent knowledge of spring Data JPA has been very good, providing a number of methods, including crud and paging, to meet the functional requirements of reality.

Altogether it provides four interfaces:

Repository: Just an identity, indicating that any inherited it is a warehouse interface class, convenient spring automatic scanning recognition
Crudrepository: Inheriting repository, implementing a set of CRUD-related methods
Pagingandsortingrepository: Inherit crudrepository, implement a component page sort related method
Jparepository: Inheriting pagingandsortingrepository, implementing a set of JPA specification-related methods
Jpaspecificationexecutor: A relatively special, non-repository system to implement a set of JPA criteria query-related methods

I wrote the example:

/* * @RepositoryDefinition (DomainClass = User.class,idclass = integer.class)//Use this note to replace extends Repository */public inte Rface Userrepository extends Crudrepository<user, integer>{/* Repository interface, he is an empty interface, just an identity *///HQL operation is an object, and The SQL operation is a table, so here user refers to the class//can directly use some of the methods provided by repository, but the method must be named to follow certain rules, such as Findbyxx,findbyxxlike,findbyxxstartingwith
	The. Public User findbyuname (String uname);
	Use @Query annotations to solve the hassle of defining rules and implement complex queries, with more @Query in work ("Select O from User o") public list<user> showusers ();
	@Query ("Select O from user o where O.uno =? 1 and o.uname =? 2") Public User finduser (int uno,string uname); With @modifying annotations and transactions, you can complete the update and delete operations, JPQL does not support the increased Operation @Modifying @Query ("Delete from User where Uno=:uno") the public void Deluser (
	@Param ("uno") int uno); @Modifying @Query ("Update User o set o.uname =: uname where Uno =: Uno") public void Upduser (@Param ("uno") int Uno, @Param ("uname")	
	String uname); /* * Crudrepository interface Inherits Repository, provides a set of crud-related methods to test the FindOne method directly in the test class */}

The Crudrepository Interface source code provides the method:

<s extends t> s save (s entity);
<s extends t> iterable<s> Save (iterable<s> entities);
T FindOne (ID ID);
Boolean exists (ID ID);
Iterable<t> findAll ();
Iterable<t> FindAll (iterable<id> IDs);
Long count ();
VOID Delete (ID ID);
void Delete (T entity);
void Delete (iterable<? extends t> entities);
void DeleteAll ();

Take the FindOne () method as an example to test in a unit test

public class Userrepositorytest {
	private applicationcontext CTX = null;
	Private userrepository userrepository = null;
	@Before public
	void SetUp () {
		CTX = new Classpathxmlapplicationcontext ("Beans.xml");
		Userrepository = Ctx.getbean (userrepository.class);
		SYSTEM.OUT.PRINTLN ("Setup");
	}
	@After public
	void TearDown () {
		ctx = null;
		System.out.println ("teardown");
	}
	@Test public
	void TestQuery3 () {
		System.out.println ("start");
		User user = Userrepository.findone (1);
		System.out.println (User.tostring ());
		System.out.println ("Started");
	}

}