基于springboot2集成jpa,创建dao的案例

基于springboot2集成jpa,创建dao的案例

springboot中集成jpa需要再pom文件中添加jpa的jar包，使用springboot的话iju不用自己规定版本号了，自动管理依赖版本即可。

org.springframework.boot

spring-boot-starter-data-jpa

然后我们再添加hibernate和oracle的jar包，同样自动管理版本。

org.hibernate

hibernate-core

com.oracle

ojdbc6

11.2.0.4.0

然后我们在配置文件中添加jpa和链接数据库的信息。

spring.datasource.driver-class-name=oracle.jdbc.OracleDriver

spring.datasource.url=jdbc:oracle:thin:@DESKTOP-46DMVCH:1521:orcl

spring.datasource.password=****

spring.datasource.username=****

spring.mvc.date-format=yyyy-MM-dd HH:mm:ss

spring.jpa.database=oracle

spring.jpa.hibernate.ddl-auto=update

spring.jpa.show-sql=true

spring.datasource.log-abandoned=true

spring.datasource.remove-abandoned=true

spring.datasource.remove-abandoned-timeout=200

添加完成之后我们开始创建jpa使用的公共Repository,创建一个接口。这里的接口可以直接继承JpaRepository，或者可以继承别的Repository.注意要加上@NoRepositoryBean注解，告诉Spring数据：不要创建该接口实例。

当我们在下面使用dao的时候再进行创建实例

@NoRepositoryBean

public interface BaseRepository extends JpaRepository {

}

现在我们创建好了这基础的Repository如果有自己想封装的公用方法的话就可以添加到这个接口中，进行约束。

当我们创建dao接口的时候，直接继承这个基础的Repository;继承之后这个dao再spring中默认识别为一个Repository。

public interface TbUserDao extends BaseRepository {

}

下面我们就可以直接再service中注入这个dao。

@Service

public class UserService {

@Resource

private TbUserDao userDao;

}

现在我们看一下JpaRepository源码，其中继承了PagingAndSortingRepository和QueryByExampleExecutor，也就是里面直接有了各种查询的方法，并且在这两个基础上添加了保存和删除的方法。

@NoRepositoryBean

public interface JpaRepository extends PagingAndSortingRepository, QueryByExampleExecutor {

/*

* (non-javadoc)

* @see org.springframework.data.repository.CrudRepository#findAll()

*/

List findAll();

/*

* (non-Javadoc)

* @see org.springframework.data.repository.PagingAndSortingRepository#findAll(org.springframework.data.domain.Sort)

*/

List findAll(Sort sort);

/*

* (non-Javadoc)

WxcVbBWoIi * @see org.springframework.data.repository.CrudRepository#findAll(java.lang.Iterable)

*/

List findAllById(Iterable ids);

/*

* (non-Javadoc)

* @see org.springframework.data.repository.CrudRepository#save(java.lang.Iterable)

*/

List saveAll(Iterable entities);

/**

* Flushes all pending changes to the database.

*/

void flush();

/**

* Saves an entity and flushes changes instantly.

*

* @param entity

* @return the saved entity

*/

S saveAndFlush(S entity);

/**

* Deletes the given entities in a batch which means it will create a single {@link Query}. Assume that we will clear

* the {@link javax.persistence.EntityManager} after the call.

*

* @param entities

*/

void deleteInBatch(Iterable entities);

/**

* Deletes all entities in a batch call.

*/

void deleteAllInBatch();

/**

* Returns a reference to the entity with the given identifier.

*

* @param id must not be {@literal null}.

* @return a reference to the entity with the given identifier.

* @see EntityManager#getReference(Class, Object)

* @throws javax.persistence.EntityNotFoundException if no entity exists for given {@code id}.

*/

T getOne(ID id);

/*

* (non-Javadoc)

* @see org.springframework.data.repository.query.QueryByExampleExecutor#findAll(org.springframework.data.domain.Example)

*/

@Override

List findAll(Example example);

/*

* (non-Javadoc)

* @see org.springframework.data.repository.query.QueryByExampleExecutor#findAll(org.springframework.data.domain.Example, org.springframework.data.domain.Sort)

*/

@Override

List findAll(Example example, Sort sort);

}

我们再看Jpa继承的两个接口中的代码,PagingAndSortingRepository是继承了CrudRepository的，这个CrudRepository中同样有删除保存查询等方法，是比较全的，但是如果我们直接使用这个CrudRepository的话里面的查询是没有分页的方法。

而PagingAndSortingRepository是在基础上新加了分页查询的方法。

所以我们没有直接使用CrudRepository

@NoRepositoryBean

public interface PagingAndSortingRepository extends CrudRepository {

Iterable findAll(Sort var1);

Page findAll(Pageable var1);

}

会有疑问的是我们这里的接口为什么可以直接注入。

因为当我们运行项目的时候，spring识别这个dao是一个Repository会自动为这个接口创建一个接口名+Impl的实现类,如下例子中的就是生成TbUserDaoImpl的实现类。

这个我们可以在EnableJpaRepositories注解源码中可以看到。

里面的repositoryImplementationPostfix()方法是定义repository接口生成的实现类后缀是什么，springboot默认帮我们定义成了Impl。

我们也可以在springboot启动类上面使用这个注解自己定义这个值。

@Target(ElementType.TYPE)

@Retention(RetentionPolicy.RUNTIME)

@Documented

@Inherited

@Import(JpaRepositoriesRegistrar.class)

public @interface EnableJpaRepositories {

/**

* Alias for the {@link #basePackages()} attribute. Allows for more concise annotation declarations e.g.:

* {@code @EnableJpaRepositories("org.my.pkg")} instead of {@code @EnableJpaRepositories(basePackages="org.my.pkg")}.

*/

String[] value() default {};

/**

* Base packages to scan for annotated components. {@link #value()} is an alias for (and mutually exclusive with) this

* attribute. Use {@link #basePackageClasses()} for a type-safe alternative to String-based package names.

*/

String[] basePackages() default {};

/**

* Type-safe alternative to {@link #basePackages()} for specifying the packages to scWxcVbBWoIian for annotated components. The

* package of each class specified will be scanned. Consider creating a special no-op marker class or interface in

* each package that serves no purpose other than being referenced by this attribute.

*/

Class>[] basePackageClasses() default {};

/**

* Specifies which types are eligible for component scanning. Further narrows the set of candidate components from

* everything in {@link #basePackages()} to everything in the base packages that matches the given filter or filters.

*/

Filter[] includeFilters() default {};

/**

* Specifies which types are not eligible for component scanning.

*/

Filter[] excludeFilters() default {};

/**

* Returns the postfix to be used when looking up custom repository implementations. Defaults to {@literal Impl}. So

* for a repository named {@code PersonRepository} the corresponding implementation class will be looked up scanning

* for {@code PersonRepositoryImpl}.

*

* @return

*/

String repositoryImplementationPostfix() default "Impl";

/**

* Configures the location of where to find the Spring Data named queries properties file. Will default to

* {@code META-INF/jpa-named-queries.properties}.

*

* @return

*/

String namedQueriesLocation() default "";

/**

* Returns the key of the {@link QueryLookupStrategy} to be used for lookup queries for query methods. Defaults to

* {@link Key#CREATE_IF_NOT_FOUND}.

*

* @return

*/

Key queryLookupStrategy() default Key.CREATE_IF_NOT_FOUND;

/**

* Returns the {@link FactoryBean} class to be used for each repository instance. Defaults to

* {@link JpaRepositoryFactoryBean}.

*

* @return

*/

Class> repositoryFactoryBeanClass() default JpaRepositoryFactoryBean.class;

/**

* Configure the repository base class to be used to create repository proxies for this particular configuration.

*

* @return

* @since 1.9

*/

Class> repositoryBaseClass() default DefaultRepositoryBaseClass.class;

// JPA specific configuration

/**

* Configures the name of the {@link EntityManagerFactory} bean definition to be used to create repositories

* discovered through this annotation. Defaults to {@code entityManagerFactory}.

*

* @return

*/

String entityManagerFactoryRef() default "entityManagerFactory";

/**

* Configures the name of the {@link PlatformTransactionManager} bean definition to be used to create repositories

* discovered through this annotation. Defaults to {@code transactionManager}.

*

* @return

*/

String transactionManagerRef() default "transactionManager";

/**

* Configures whether nested repository-interfaces (e.g. defined as inner classes) should be discovered by the

* repositories infrastructure.

*/

boolean considerNestedRepositories() default false;

/**

* Configures whether to enable default transactions for Spring Data JPA repositories. Defaults to {@literal true}. If

* disabled, repositories must be used behind a facade that's configuring transactions (e.g. using Spring's annotation

* driven transaction facilities) or repository methods have to be used to demarcate transactions.

*

* @return whether to enable default transactions, defaults to {@literal true}.

*/

boolean enableDefaultTransactions() default true;

}

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