Spring Data Jpa implement CRUD

First, create a Maven project

Second, implement CRUD

  Creating Tools

package cn.kgc.utils;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

public class Jpautil {
    private static EntityManagerFactory factory;
    static {
        //根据Persistence创建 EntityManagerFactory对象
        factory = Persistence.createEntityManagerFactory("myjpa");
    }

    //获得EntityManager对象的方法
    public static EntityManager getEntityManager(){
        EntityManager entityManager = factory.createEntityManager();
        return entityManager;
    }
}

 

1, add data

persist () method for adding a data

// add data 
    @Test
     public  void firstTest () { 

        // get the object by tools EntityTransaction 
        the EntityManager entityManager = Jpautil.getEntityManager ();
         // get business objects 
        EntityTransaction Transaction = entityManager.getTransaction ();
         // open things 
        transaction.begin ();
         // create an entity class object, 10 pieces of information 
        for ( int I = 0; I <10; I ++ ) { 
            the Customer Customer = new new the Customer (); 
            customer.setName ( "Liugao Yang" ); 
            customer.setSex ("Male" ); 
            customer.setAge ( 18 ); 
            customer.setAddres ( "Zhengzhou City" );
             // 5 Using Entitymanager objects persist ways to add data to the database 
            EntityManager.persist (the Customer); 
        } 
        // submit things 
        transaction.commit ();
         // close the connection 
        entityManager.close ();
 //         factory.close (); 

    }

 

2, based on the id query data

　　find method

　　getReference () 方法

// According to query the data id
     //     use the find method to query the database
     //         features:
     //             1, the object is to query the current object itself itself
     //             2, sql statement will be sent when you call the find method
     // This method is called immediately loading 
    @Test
     public  void testFind () {
         // get entityManager core object is the object to operate the database 
        the entityManager entityManager = Jpautil.getEntityManager ();
         // get EntityTransaction business objects 
        the EntityTransaction EntityTransaction = entityManager.getTransaction ();
         // open things 
        entityTransaction.begin ();
         // execute query method id
        = EntityManager.find the Customer the Customer (the Customer. Class , 3 ); 
        System.out.println (the Customer); 
        // submit things 
        entityTransaction.commit ();
         // close the core classes, the release of resources 
        entityManager.close (); 
    } 

// according to query data id
     //     use getReference method
     //         features:
     //             1, the method of inquiry is a dynamic proxy object
     //             2, when performing Reference method does not print sql statement to query the database immediately, but call the query object will call sql statement,
     //     ie, when to send sql statement to query the database with when
     // the way to becoming lazy loading or lazy loading 
    @Test
     public  void testReference () {
        // get entityManager of the object to the object is the core operation of the database 
        the EntityManager entityManager = Jpautil.getEntityManager ();
         // get things entityTransaction target 
        the EntityTransaction entityTransaction = entityManager.getTransaction ();
         // turn things 
        entityTransaction.begin ();
         // execution the method id query 
        the Customer the Customer = entityManager.getReference (the Customer. class , 1 ); 
        System.out.println (the Customer); 
        // submit things 
        entityTransaction.commit ();
         // close the core classes, the release of resources 
        entityManager.close ( ); 
    }

3, the method for modifying data

　　After the merge () method for modifying data stored database

// modify data merge () save the modified data 
    @Test
     public  void testmerge () {
         // get entityManager core object is the object to operate the database 
        the EntityManager entityManager = Jpautil.getEntityManager ();
         // get entityTransaction business objects 
        EntityTransaction = the EntityTransaction entityManager.getTransaction ();
         // turn things 
        entityTransaction.begin ();
         // execute query id method according to 
        the Customer the Customer = entityManager.getReference (the Customer. class , 2 ); 
        customer.setName ( "Cao Cao" ); 
        entityManager .merge (customer);
        System.out.println (the Customer); 
        // submit things 
        entityTransaction.commit ();
         // close the core classes, the release of resources 
        entityManager.close (); 
    }

 

4, delete data

　　remove () method is used to delete database data

// delete data Case 
    @Test
     public  void testRemove () {
         // get entityManager of the object to the object is the core operation of the database 
        the EntityManager entityManager = Jpautil.getEntityManager ();
         // get things entityTransaction target 
        the EntityTransaction entityTransaction = entityManager.getTransaction ();
         // turn things 
        entityTransaction.begin ();
         // execute query id method according to 
        the Customer Customer1 = EntityManager.find (the Customer. class , 3 );
         // delete operation 
        the EntityManager.remove (Customer1); 
        System.out.println ( customer1);
        // submit things 
        entityTransaction.commit ();
         // close the core classes, the release of resources 
        entityManager.close (); 
    }

 

5, all queries based on jpql

// query all based jpql create 
@Test
 public  void findAll () {
     // get the object entityManager 
    the EntityManager entityManager = Jpautil.getEntityManager ();
     //   based jpql Query object created from the get entityManager
     // SQL statement: "select * from Customer" Customer here refers to the table
     // JPQL statement: "from Customer" means to query all of the data entity class Customer, Customer's worth here is the entity class 
    query query = entityManager.createQuery ( "from Customer" );
     // getResultList () method: this method is a method query objects, the query returns a collection of data objects 
    List <the Customer> = resultList query.getResultList ();
     for (Customer the Customer: resultList) {
        System.out.println (Customer); 
    } 
    //Close the connection 
    entityManager.close (); 

}

 

6, based on jpql paging query

setFirstResult () represents the beginning of a query from the first few

setMaxResults () represents the number of page impressions

// set page information 
@Test
 public  void fianAllWithPage () {
     // create entityManager 
    the EntityManager entityManager = Jpautil.getEntityManager ();
     // get query object
     // "from Customer" means that all of the data entity class Customer queries, where the Customer entity class is worth 
    query query = entityManager.createQuery ( "Customer from" );
     // set page information 
    query.setFirstResult (. 5); // represents a query from the first few start 
   query.setMaxResults (10); // represents each the number of page impressions
    // get all the data query and returns the set list 
    List <the Customer> = resultList query.getResultList ();
     for (Customer customer:resultList) {
        System.out.println(customer);
    }
}

 

7, according to id query based jpql

//   JPQL by id check 
@Test
 public  void findJpqlid () { 
    the EntityManager entityManager = Jpautil.getEntityManager ();
     // get query object
     // "from Customer the WHERE id =?" Representation of the object id of the query Customer 

    Query query = entityManager. the createQuery ( "from the Customer WHERE ID =?" );
     // set value placeholder. The first parameter is the position of the placeholder, the placeholder for the second parameter value 
    query.setParameter (1,1 );
     // perform queries 
    the Customer custome = (the Customer) query.getSingleResult (); 
    the System.out. the println (custome); 
    // Close the resource 
    entityManager.close (); 

}

 

8, jpql fuzzy query-based

// JPQL fuzzy query 
@Test
 public  void findJpqlByName () { 
    the EntityManager entityManager = Jpautil.getEntityManager ();
     // "?? From the Customer like Sex and the WHERE name like" means that the fuzzy query by name and gender 
    Query query = entityManager. the createQuery ( "like and from the Customer WHERE name like Sex??" );
     // set the parameters for the position of the first parameter placeholder, the placeholder for the second parameter value 
    query.setParameter (1, "% Cao % " ); 
    query.setParameter ( 2, '% M%" );
     // execute the query 
    List <the Customer> = resultList query.getResultList (); 
    System.out.println (resultList); 
    // close the resource
    entityManager.close();
}

 

9, ascending descending query based jpql

@Test
 public  void findAllByOrder () { 
    the EntityManager entityManager = Jpautil.getEntityManager (); 
    Query Query = entityManager.createQuery ( "Order from the Customer ID by desc"); // desc for descending query,
 //   Query Query entityManager.createQuery = ( "Order from the Customer ID by ASC"); // ASC for ascending query
 // getResultList () method returns a query List of all data objects set 
    List <the Customer> = resultList query.getResultList ();
     for (Customer the Customer: resultList) { 
        System.out.println (Customer); 
    } 
    entityManager.close (); 
}

 

10, a query based on aggregate functions jpql

//   aggregate function 
@Test
 public  void findAllCount () { 
    the EntityManager entityManager = Jpautil.getEntityManager (); 
    Query Query = entityManager.createQuery ( "SELECT COUNT (*) from Customer"); // lookup table a column how many Customer Information
     // this method indicates the number of statistics 
    Object Customer = query.getSingleResult (); 
    System.out.println (Customer); 
    entityManager.close (); 
}