使用 JPA, Jersey 从数据库中检索 Blob(pdf)

Question

我有一个在后端使用 JPA-REST 的 JSP 页面，我已经设法将一个 blob 插入到数据库中。现在我希望能够从数据库中 检索/获取 blob，但我似乎找不到任何示例来说明如何通过 Jersey 而不是使用 servlet（我'我对创建自己的 REST 服务还很陌生。

这是我用来向数据库插入 blob 的代码：

@POST
@Path("upload/{id}")
@Consumes({"application/x-www-form-urlencoded", "multipart/form-data"})
public void addBlob(@PathParam("id") Integer id, @FormDataParam("file") InputStream uploadedInputStream) throws IOException {
    ClientCaseDoc entityToMerge = find(id);
    try {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int read = 0;
        byte[] bytes = new byte[1024];
        while ((read = uploadedInputStream.read(bytes)) != -1) {
            out.write(bytes, 0, read);
        }
        entityToMerge.setDocument(out.toByteArray());
        super.edit(entityToMerge);
    }
    catch (IOException e) {
        e.printStackTrace();
    }
}

是否有任何类似的方法可以从数据库中检索 blob？还是必须使用 servlet？

非常感谢任何帮助。

Answer 1

这已经得到回答，但可以帮助解决更广泛的问题；

我有一个实体；

@Entity
public class BlobEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column(name = "NAME")
    private String name;

    @Lob
    @Column(name="DATA", length=100000)
    private byte[] data;

JPA 存储库

@Repository
public interface BlobEntityRepository extends CrudRepository<BlobEntity, Long> {
}

以及读取 word 文档并从数据库中检索它的测试

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:applicationContext-test.xml")
public class BlobEntitytRepositoryTest extends AbstractTest {

    @Autowired
    private BlobEntityRepository repository;

    @Test
    @Transactional
    public void test1() throws IOException {

        InputStream inputStream = getClass().getResourceAsStream("/HelloGreg.docx");
        byte[] byteArray = IOUtils.toByteArray(inputStream);

        BlobEntity blobEntity = new BlobEntity();
        blobEntity.setName("test");
        blobEntity.setData(byteArray);

        repository.save(blobEntity);

        assertEquals(1, repository.count());

        BlobEntity entity = repository.findOne(1l);
        assertNotNull(entity);

        FileOutputStream outputStream = new FileOutputStream(new File("testOut.docx"));
        IOUtils.write(entity.getData(), outputStream);
    }

}

配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:jdbc="http://www.springframework.org/schema/jdbc"
    xmlns:jpa="http://www.springframework.org/schema/data/jpa" xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:cache="http://www.springframework.org/schema/cache"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd
    http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc.xsd
    http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa.xsd
    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
    http://www.springframework.org/schema/cache http://www.springframework.org/schema/cache/spring-cache.xsd">

    <context:component-scan base-package="com.greg" />
    <tx:annotation-driven />
    <jpa:repositories base-package="com.greg" />

    <bean id="dataSource"
        class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="org.h2.Driver" />
        <property name="url" value="jdbc:h2:file:~/data/jpa-test" />
        <property name="username" value="sa" />
        <property name="password" value="" />
    </bean>

    <bean id="entityManagerFactory"
        class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="dataSource" ref="dataSource" />
        <property name="packagesToScan" value="com.greg" />
        <property name="jpaVendorAdapter">
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter" />
        </property>
        <property name="jpaProperties">
            <props>
                <prop key="hibernate.hbm2ddl.auto">create</prop>
                <prop key="hibernate.show_sql">false</prop>
                <prop key="hibernate.dialect">org.hibernate.dialect.H2Dialect</prop>
            </props>
        </property>
    </bean>

    <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactory" />
    </bean>

</beans>

Answer 2

Is there any similar way of Retrieving a blob from the database? Or do I have to use servlets?

虽然问题中没有提到，但我认为这是关于通过 Jersey 而不是使用 Servlet 返回 BLOB。 OP，如果我错了，请在评论中纠正我。如果我是对的，您可能希望更新您的问题以提及泽西岛。

这道题我觉得和Input and Output binary streams using JERSEY?. However the comments appear to show some confusion as to how to implement it in the OPs case. As you are loading the PDFs in the domain model (if that is a good thing I'll let other people argue over) streaming is not needed. All you need to do is create a Response with the entity设置为数据层返回的字节数组是重复的

@Path("upload/{id}")
@GET
public Response getPDF(@PathParam("id") Integer id) throws Exception {
    ClientCaseDoc entity = find(id);
    return Response
            .ok()
            .type("application/pdf")
            .entity(entity.getDocument()) // Assumes document is a byte array in the domain object.
            .build();
}

使用 JPA, Jersey 从数据库中检索 Blob(pdf)

Retrieve Blob(pdf) from database using JPA, Jersey

java

rest

jpa

blob