基于springboot2集成jpa,創(chuàng)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的話iju不用自己規(guī)定版本號了,自動管理依賴版本即可。
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency>
然后我們再添加hibernate和oracle的jar包,同樣自動管理版本。
<dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-core</artifactId> </dependency> <dependency> <groupId>com.oracle</groupId> <artifactId>ojdbc6</artifactId> <version>11.2.0.4.0</version> </dependency>
然后我們在配置文件中添加jpa和鏈接數據庫的信息。
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
添加完成之后我們開始創(chuàng)建jpa使用的公共Repository,創(chuàng)建一個接口。這里的接口可以直接繼承JpaRepository,或者可以繼承別的Repository.注意要加上@NoRepositoryBean注解,告訴Spring數據:不要創(chuàng)建該接口實例。
當我們在下面使用dao的時候再進行創(chuàng)建實例
@NoRepositoryBean public interface BaseRepository<T> extends JpaRepository<T,Long> { }
現在我們創(chuàng)建好了這基礎的Repository如果有自己想封裝的公用方法的話就可以添加到這個接口中,進行約束。
當我們創(chuàng)建dao接口的時候,直接繼承這個基礎的Repository;繼承之后這個dao再spring中默認識別為一個Repository。
public interface TbUserDao extends BaseRepository<TbUser> { }
下面我們就可以直接再service中注入這個dao。
@Service public class UserService { @Resource private TbUserDao userDao; }
現在我們看一下JpaRepository源碼,其中繼承了PagingAndSortingRepository和QueryByExampleExecutor,也就是里面直接有了各種查詢的方法,并且在這兩個基礎上添加了保存和刪除的方法。
@NoRepositoryBean public interface JpaRepository<T, ID> extends PagingAndSortingRepository<T, ID>, QueryByExampleExecutor<T> { /* * (non-Javadoc) * @see org.springframework.data.repository.CrudRepository#findAll() */ List<T> findAll(); /* * (non-Javadoc) * @see org.springframework.data.repository.PagingAndSortingRepository#findAll(org.springframework.data.domain.Sort) */ List<T> findAll(Sort sort); /* * (non-Javadoc) * @see org.springframework.data.repository.CrudRepository#findAll(java.lang.Iterable) */ List<T> findAllById(Iterable<ID> ids); /* * (non-Javadoc) * @see org.springframework.data.repository.CrudRepository#save(java.lang.Iterable) */ <S extends T> List<S> saveAll(Iterable<S> entities); /** * Flushes all pending changes to the database. */ void flush(); /** * Saves an entity and flushes changes instantly. * * @param entity * @return the saved entity */ <S extends T> 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<T> 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 <S extends T> List<S> findAll(Example<S> example); /* * (non-Javadoc) * @see org.springframework.data.repository.query.QueryByExampleExecutor#findAll(org.springframework.data.domain.Example, org.springframework.data.domain.Sort) */ @Override <S extends T> List<S> findAll(Example<S> example, Sort sort); }
我們再看Jpa繼承的兩個接口中的代碼,PagingAndSortingRepository是繼承了CrudRepository的,這個CrudRepository中同樣有刪除保存查詢等方法,是比較全的,但是如果我們直接使用這個CrudRepository的話里面的查詢是沒有分頁的方法。
而PagingAndSortingRepository是在基礎上新加了分頁查詢的方法。
所以我們沒有直接使用CrudRepository
@NoRepositoryBean public interface PagingAndSortingRepository<T, ID> extends CrudRepository<T, ID> { Iterable<T> findAll(Sort var1); Page<T> findAll(Pageable var1); }
會有疑問的是我們這里的接口為什么可以直接注入。
因為當我們運行項目的時候,spring識別這個dao是一個Repository會自動為這個接口創(chuàng)建一個接口名+Impl的實現類,如下例子中的就是生成TbUserDaoImpl的實現類。
這個我們可以在EnableJpaRepositories注解源碼中可以看到。
里面的repositoryImplementationPostfix()方法是定義repository接口生成的實現類后綴是什么,springboot默認幫我們定義成了Impl。
我們也可以在springboot啟動類上面使用這個注解自己定義這個值。
@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 scan 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; }
以上為個人經驗,希望能給大家一個參考,也希望大家多多支持腳本之家。如有錯誤或未考慮完全的地方,望不吝賜教。
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