SpringDataJPA

介绍：

spirng data jpa是spring提供的一套简化JPA开发的框架，按照约定好的规则进行【方法命名】去写dao层接口，就可以在不写接口实现的情况下，实现对数据库的访问和操作。同时提供了很多除了CRUD之外的功能，如分页、排序、复杂查询等等。

Spring Data JPA 让我们解脱了DAO层的操作，基本上所有CRUD都可以依赖于它来实现,在实际的工作工程中，推荐使用Spring Data JPA + ORM（如：hibernate）完成操作，这样在切换不同的ORM框架时提供了极大的方便，同时也使数据库层操作更加简单，方便解耦。

SpringData Jpa 极大简化了数据库访问层代码。 如何简化的呢？ 使用了SpringDataJpa，我们的dao层中只需要写接口，就自动具有了增删改查、分页查询等方法。

示例：

pom依赖：

依赖1：

最好在父maven项目中设置spring data统一版本管理依赖: 因为不同的spring data子项目发布时间版本不一样，你自己维护很麻烦， 这样不同的spring data子项目能保证是统一版本

    org.springframework.data
    spring-data-bom
    2021.1.0
    import
    pom

 子项目依赖：

    org.springframework.data
    spring-data-jpa




    junit
    junit
    4.13
    test



    org.hibernate
    hibernate-entitymanager
    5.4.32.Final




    mysql
    mysql-connector-java
    5.1.22




    com.alibaba
    druid
    1.2.8




    org.springframework
    spring-test
    5.3.10
    test

javaconfig:

@Configuration          // 标记当前类为配置类   =xml配文件
//@EnableJpaRepositories(basePackages="com.tuling.repositories")  // 启动jpa    
    
        
        
        
        
    
    * */
    @Bean
    public DataSource dataSource() {

        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setUsername("root");
        dataSource.setPassword("123456");
        dataSource.setDriverClassName("com.mysql.jdbc.Driver");
        dataSource.setUrl("jdbc:mysql://localhost:3306/springdata_jpa?characterEncoding=UTF-8");

        return  dataSource;

    }

    /*
    *  
    
        
            
            
                
                
                
            
        
        
        
        
    
    * */
    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {

        HibernateJpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        vendorAdapter.setGenerateDdl(true);
        vendorAdapter.setShowSql(true);

        LocalContainerEntityManagerFactoryBean factory = new LocalContainerEntityManagerFactoryBean();
        factory.setJpaVendorAdapter(vendorAdapter);
        factory.setPackagesToScan("com.tuling.pojo");
        factory.setDataSource(dataSource());
        return factory;
    }

    /*
    * 
        
    
    * */
    @Bean
    public PlatformTransactionManager transactionManager(EntityManagerFactory entityManagerFactory) {

        JpaTransactionManager txManager = new JpaTransactionManager();
        txManager.setEntityManagerFactory(entityManagerFactory);
        return txManager;
    }

}

spring.xml

pojo实体类：

@Entity     // 作为hibernate 实体类
@Table(name = "tb_customer")       // 映射的表明
public class Customer {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private Long custId; //客户的主键

    @Column(name = "cust_name")
    private String custName;//客户名称

    @Column(name="cust_address")
    private String custAddress;//客户地址

    public Long getCustId() {
        return custId;
    }

    public void setCustId(Long custId) {
        this.custId = custId;
    }

    public String getCustName() {
        return custName;
    }

    public void setCustName(String custName) {
        this.custName = custName;
    }

    public String getCustAddress() {
        return custAddress;
    }

    public void setCustAddress(String custAddress) {
        this.custAddress = custAddress;
    }

    @Override
    public String toString() {
        return "Customer{" +
                "custId=" + custId +
                ", custName='" + custName + '\'' +
                ", custAddress='" + custAddress + '\'' +
                "}\n";
    }
}

customerRepository:

public interface CustomerRepository extends CrudRepository{
// public interface CustomerRepository extends PagingAndSortingRepository{
  }

测试：

//@ContextConfiguration("/spring.xml")
@ContextConfiguration(classes = SpringDataJPAConfig.class)
@RunWith(SpringJUnit4ClassRunner.class)
public class SpringdataJpaTest {

    // jdk动态代理的实例
    @Autowired
    CustomerRepository repository;

    @Test
    public  void testR(){
        Optional byId = repository.findById(20L);
            System.out.println(byId.orElse(null));
    }

    @Test
    public  void testC(){
        Customer customer = new Customer();
        customer.setCustName("李四");
        System.out.println(repository.save(customer));
    }

    @Test
    public  void testD(){
        Customer customer = new Customer();
        customer.setCustId(3L);
        customer.setCustName("李四");
        repository.delete(customer);
    }

    @Test
    public  void testFindAll(){
        Iterable allById = repository.findAllById(Arrays.asList(1L, 7L, 8L));
        System.out.println(allById);
    }
}

CrudRepository与PagingAndSortingRepository区别：

PagingAndSortingRepository更全，除了CrudRepository的东西，里面包含分页。

 

 PagingAndSortingRepository的实例测试：

@ContextConfiguration(classes = SpringDataJPAConfig.class)
@RunWith(SpringJUnit4ClassRunner.class)
public class SpringDataJpaPagingAndSortTest
{
    // jdk动态代理的实例
    @Autowired
    CustomerRepository repository;

    @Test
    public  void testPaging(){
        Page all = repository.findAll(PageRequest.of(0, 2));
        System.out.println(all.getTotalPages());
        System.out.println(all.getTotalElements());
        System.out.println(all.getContent());

    }

    @Test
    public  void testSort(){
        Sort sort = Sort.by("custId").descending();
        Iterable all = repository.findAll(sort);
        System.out.println(all);
    }


    @Test
    public  void testSortTypeSafe(){

        Sort.TypedSort sortType = Sort.sort(Customer.class);

        Sort sort = sortType.by(Customer::getCustId).descending();
        Iterable all = repository.findAll(sort);

        System.out.println(all);

    }
}

自定义操作

jpql(原生sql)：

a. @Query

i. 查询如果返回单个实体 就用pojo接收 ， 如果是多个需要通过集合

ii. 参数设置方式1. 索引 ： ?数字2. 具名： :参数名 结合@Param注解指定参数名字

iii. 增删改：1. 要加上事务的支持：2. 如果是插入方法：一定只能在hibernate下才支持 （Insert into..select )

@Transactional

@Modifying // 通知springdatajpa 是增删改的操作

CustomerRepository:

public interface CustomerRepository extends PagingAndSortingRepository{
//public interface CustomerRepository extends CrudRepository{
    // 增删查改

    // 查询
    @Query("FROM Customer where custName=:custName ")
    List findCustomerByCustName(@Param("custName") String custName);

    // 修改
    @Transactional
    @Modifying   // 通知springdatajpa 是增删改的操作
    @Query("UPDATE Customer c set c.custName=:custName where c.custId=:id")
    int updateCustomer(@Param("custName") String custName,@Param("id")Long id);


    @Transactional
    @Modifying   // 通知springdatajpa 是增删改的操作
    @Query("DELETE FROM Customer c where c.custId=?1")
    int deleteCustomer(Long id);

    // 新增  JPQL
    @Transactional
    @Modifying   // 通知springdatajpa 是增删改的操作
    @Query("INSERT INTO Customer (custName) SELECT c.custName FROM Customer c where c.custId=?1")
    int insertCustomerBySelect(Long id);


    @Query(value="select * FROM tb_customer where cust_name=:custName "
    ,nativeQuery = true)
    List findCustomerByCustNameBySql(@Param("custName") String custName);
}

 测试：

@ContextConfiguration(classes = SpringDataJPAConfig.class)
@RunWith(SpringJUnit4ClassRunner.class)
public class JpqlTest {

    // jdk动态代理的实例
    @Autowired
    CustomerRepository repository;

    @Test
    public  void testR(){
        List customer = repository.findCustomerByCustName("李四");
        System.out.println(customer);
    }

    @Test
    public  void testU(){
        int result = repository.updateCustomer("王五", 7L);
        System.out.println(result);
    }

    @Test
    public  void testD(){
        int result = repository.deleteCustomer(10L);
        System.out.println(result);
    }

    @Test
    public  void testC(){
        int result = repository.insertCustomerBySelect(7L);
        System.out.println(result);
    }

    @Test
    public  void testR_sql(){
        List customer = repository.findCustomerByCustNameBySql("徐庶");
        System.out.println(customer);
    }
}

规定方法名：

支持的查询方法主题关键字(前缀)

决定当前方法作用

只支持查询 和删除

支持的查询方法谓词关键字和修饰符

决定查询条件

 

 CustomerMethodNameRepository：：

public interface CustomerMethodNameRepository extends PagingAndSortingRepository {

     List findByCustName(String custName);

     boolean existsByCustName(String custName);


     @Transactional
     @Modifying
     int deleteByCustId(Long custName);

     List findByCustNameLike(String custName);

}

测试：

@ContextConfiguration(classes = SpringDataJPAConfig.class)
@RunWith(SpringJUnit4ClassRunner.class)
public class MethodNameTest {

    // jdk动态代理的实例
    @Autowired
    CustomerMethodNameRepository repository;

    @Test
    public  void test01() {
        List list = repository.findByCustName("李四");
        System.out.println(list);
    }

    @Test
    public  void test02() {
        boolean exists = repository.existsByCustName("xxx");
        System.out.println(exists);
    }

    @Test
    public  void test03() {
        int exists = repository.deleteByCustId(12L);
        System.out.println(exists);
    }


    @Test
    public  void test04() {
        List list = repository.findByCustNameLike("徐%");
        System.out.println(list);
    }
}

Query by Example:

只支持查询：

i. 不支持嵌套或分组的属性约束，如 firstname = ？0 or (firstname = ？1and lastname = ？2).

ii. 只支持字符串 start/contains/ends/regex 匹配和其他属性类型的精确匹配。

实现：将Repository继承QueryByExampleExecutor

实例：

CustomerQBERepository：

public interface CustomerQBERepository
        extends PagingAndSortingRepository
          , QueryByExampleExecutor {
}

测试：

@ContextConfiguration(classes = SpringDataJPAConfig.class)
@RunWith(SpringJUnit4ClassRunner.class)
public class QBETest {

    // jdk动态代理的实例
    @Autowired
    CustomerQBERepository repository;

    /**
     * 简单实例  客户名称  客户地址动态查询
     */
    @Test
    public  void test01(){

        // 查询条件
        Customer customer=new Customer();
        customer.setCustName("徐庶");
        customer.setCustAddress("BEIJING");

        // 通过Example构建查询条件
        Example example = Example.of(customer);

        List list = (List) repository.findAll(example);
        System.out.println(list);
    }


    /**
     *  通过匹配器 进行条件的限制
     * 简单实例  客户名称  客户地址动态查询
     */
    @Test
    public  void test02(){

        // 查询条件
        Customer customer=new Customer();
        customer.setCustName("庶");
        customer.setCustAddress("JING");

        // 通过匹配器 对条件行为进行设置
        ExampleMatcher matcher = ExampleMatcher.matching()
                //.withIgnorePaths("custName")       // 设置忽略的属性
                //.withIgnoreCase("custAddress")      // 设置忽略大小写
                //.withStringMatcher(ExampleMatcher.StringMatcher.ENDING);    // 对所有条件字符串进行了结尾匹配
                .withMatcher("custAddress",m -> m.endsWith().ignoreCase());      // 针对单个条件进行限制, 会使withIgnoreCase失效，需要单独设置
                //.withMatcher("custAddress", ExampleMatcher.GenericPropertyMatchers.endsWith().ignoreCase());

        // 通过Example构建查询条件
        Example example = Example.of(customer,matcher);

        List list = (List) repository.findAll(example);
        System.out.println(list);
    }
}

Specifications:

在之前使用Query by Example只能针对字符串进行条件设置，那如果希望对所有类型支持，可以使用Specifications

实例：

实现：将Repository继承JpaSpecificationExecutor

CustomerSpecificationsRepository：

public interface CustomerSpecificationsRepository
        extends PagingAndSortingRepository,
        JpaSpecificationExecutor {

}

Root：查询哪个表（关联查询） = from

CriteriaQuery：查询哪些字段，排序是什么 =组合(order by . where )

CriteriaBuilder：条件之间是什么关系，如何生成一个查询条件，每一个查询条件都是什么类型（>between in...) = where

Predicate（Expression）： 每一条查询条件的详细描述

@ContextConfiguration(classes = SpringDataJPAConfig.class)
@RunWith(SpringJUnit4ClassRunner.class)
public class SpecificationTest {

    // jdk动态代理的实例
    @Autowired
    CustomerSpecificationsRepository repository;

    @Test
    public  void testR(){

        List customer = repository.findAll(new Specification() {
            @Override
            public Predicate toPredicate(Root root, CriteriaQuery query, CriteriaBuilder cb) {

                // root from Customer  , 获取列
                // CriteriaBuilder where 设置各种条件  (> < in ..)
                // query  组合（order by , where)

                return null;
            }
        });

        System.out.println(customer);
    }


    /**
     * 查询客户范围 (in)
     * id  >大于
     * 地址  精确
     */
    @Test
    public  void testR2(){

        List customer = repository.findAll(new Specification() {
            @Override
            public Predicate toPredicate(Root root, CriteriaQuery query, CriteriaBuilder cb) {

                // root from Customer  , 获取列
                // CriteriaBuilder where 设置各种条件  (> < in ..)
                // query  组合（order by , where)
                Path