JavaPersistenceWithHibernate第二版笔记-第五章-Mapping value types-005控制类型映射(Nationalized、@LOB、@org.hibernate.annotations.Type)

一、简介

1.

2.

3.

4.

to override this default mapping. The JPA specification has a convenient shortcut annotation for this purpose, @Lob

 @Entity
 public class Item {
     @Lob
     protected byte[] image;
     @Lob
     protected String description;
     // ...
 }

This maps the byte[] to an SQL BLOB data type and the String to a CLOB . Unfortunately, you still don’t get lazy loading with this design.

Alternatively, you can switch the type of property in your Java class. JDBC supports locator objects ( LOB s) directly. If your Java property is java.sql.Clob or java .sql.Blob , you get lazy loading without bytecode instrumentation:

 @Entity
 public class Item {
     @Lob
     protected java.sql.Blob imageBlob;
     @Lob
     protected java.sql.Clob description;
     // ...
 }

5.自定义类型

 @Entity
 public class Item {
     @org.hibernate.annotations.Type(type = "yes_no")
     protected boolean verified = false;
 }

或

 metaBuilder.applyBasicType(new MyUserType(), new String[]{"date"});

二、代码

 package org.jpwh.model.advanced;

 import org.jpwh.model.Constants;

 import javax.persistence.Access;
 import javax.persistence.AccessType;
 import javax.persistence.Basic;
 import javax.persistence.Column;
 import javax.persistence.Entity;
 import javax.persistence.EnumType;
 import javax.persistence.Enumerated;
 import javax.persistence.FetchType;
 import javax.persistence.GeneratedValue;
 import javax.persistence.Id;
 import javax.persistence.Lob;
 import javax.persistence.Temporal;
 import javax.persistence.TemporalType;
 import javax.validation.constraints.NotNull;
 import java.math.BigDecimal;
 import java.sql.Blob;
 import java.util.Date;

 @Entity
 public class Item {

     /*
        The <code>Item</code> entity defaults to field access, the <code>@Id</code> is on a field. (We
        have also moved the brittle <code>ID_GENERATOR</code> string into a constant.)
      */
     @Id
     @GeneratedValue(generator = Constants.ID_GENERATOR)
     protected Long id;

     @org.hibernate.annotations.Type(type = "yes_no")
     protected boolean verified = false;

     // JPA says @Temporal is required but Hibernate will default to TIMESTAMP without it
     @Temporal(TemporalType.TIMESTAMP)
     @Column(updatable = false)
     @org.hibernate.annotations.CreationTimestamp
     protected Date createdOn;

     // Java 8 API
     // protected Instant reviewedOn;

     @NotNull
     @Basic(fetch = FetchType.LAZY) // Defaults to EAGER
     protected String description;

     @Basic(fetch = FetchType.LAZY)
     @Column(length = 131072) // 128 kilobyte maximum for the picture
     protected byte[] image; // Maps to SQL VARBINARY type

     @Lob
     protected Blob imageBlob;

     @NotNull
     @Enumerated(EnumType.STRING) // Defaults to ORDINAL
     protected AuctionType auctionType = AuctionType.HIGHEST_BID;

     @org.hibernate.annotations.Formula(
         "substr(DESCRIPTION, 1, 12) || '...'"
     )
     protected String shortDescription;

     @org.hibernate.annotations.Formula(
         "(select avg(b.AMOUNT) from BID b where b.ITEM_ID = ID)"
     )
     protected BigDecimal averageBidAmount;

     @Column(name = "IMPERIALWEIGHT")
     @org.hibernate.annotations.ColumnTransformer(
         read = "IMPERIALWEIGHT / 2.20462",
         write = "? * 2.20462"
     )
     protected double metricWeight;

     @Temporal(TemporalType.TIMESTAMP)
     @Column(insertable = false, updatable = false)
     @org.hibernate.annotations.Generated(
         org.hibernate.annotations.GenerationTime.ALWAYS
     )
     protected Date lastModified;

     @Column(insertable = false)
     @org.hibernate.annotations.ColumnDefault("1.00")
     @org.hibernate.annotations.Generated(
         org.hibernate.annotations.GenerationTime.INSERT
     )
     protected BigDecimal initialPrice;

     /*
         The <code>@Access(AccessType.PROPERTY)</code> setting on the <code>name</code> field switches this
         particular property to runtime access through getter/setter methods by the JPA provider.
      */
     @Access(AccessType.PROPERTY)
     @Column(name = "ITEM_NAME") // Mappings are still expected here!
     protected String name;

     /*
         Hibernate will call <code>getName()</code> and <code>setName()</code> when loading and storing items.
      */
     public String getName() {
         return name;
     }

     public void setName(String name) {
         this.name =
             !name.startsWith("AUCTION: ") ? "AUCTION: " + name : name;
     }

     public Long getId() { // Optional but useful
         return id;
     }

     public String getDescription() {
         return description;
     }

     public void setDescription(String description) {
         this.description = description;
     }

     public String getShortDescription() {
         return shortDescription;
     }

     public BigDecimal getAverageBidAmount() {
         return averageBidAmount;
     }

     public double getMetricWeight() {
         return metricWeight;
     }

     public void setMetricWeight(double metricWeight) {
         this.metricWeight = metricWeight;
     }

     public Date getLastModified() {
         return lastModified;
     }

     public BigDecimal getInitialPrice() {
         return initialPrice;
     }

     public Date getCreatedOn() {
         return createdOn;
     }

     public boolean isVerified() {
         return verified;
     }

     public void setVerified(boolean verified) {
         this.verified = verified;
     }

     public byte[] getImage() {
         return image;
     }

     public void setImage(byte[] image) {
         this.image = image;
     }

     public Blob getImageBlob() {
         return imageBlob;
     }

     public void setImageBlob(Blob imageBlob) {
         this.imageBlob = imageBlob;
     }

     public AuctionType getAuctionType() {
         return auctionType;
     }

     public void setAuctionType(AuctionType auctionType) {
         this.auctionType = auctionType;
     }
 }

三、测试代码

 package org.jpwh.test.advanced;

 import org.hibernate.Session;
 import org.hibernate.engine.jdbc.StreamUtils;
 import org.jpwh.env.JPATest;
 import org.jpwh.model.advanced.Item;
 import org.testng.annotations.Test;

 import javax.persistence.EntityManager;
 import javax.transaction.UserTransaction;
 import java.io.ByteArrayInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.InputStream;
 import java.sql.Blob;
 import java.util.Random;

 import static org.testng.Assert.assertEquals;

 public class LazyProperties extends JPATest {

     @Override
     public void configurePersistenceUnit() throws Exception {
         configurePersistenceUnit("AdvancedPU");
     }

     @Test
     public void storeLoadProperties() throws Exception {
         UserTransaction tx = TM.getUserTransaction();
         try {
             tx.begin();
             EntityManager em = JPA.createEntityManager();
             Item someItem = new Item();
             someItem.setName("Some item");
             someItem.setDescription("This is some description.");
             byte[] bytes = new byte[131072];
             new Random().nextBytes(bytes);
             someItem.setImage(bytes);
             em.persist(someItem);
             tx.commit();
             em.close();
             Long ITEM_ID = someItem.getId();

             tx.begin();
             em = JPA.createEntityManager();

             Item item = em.find(Item.class, ITEM_ID);

             // Accessing one initializes ALL lazy properties in a single SELECT
             assertEquals(item.getDescription(), "This is some description.");
             assertEquals(item.getImage().length, 131072); // 128 kilobytes

             tx.commit();
             em.close();
         } finally {
             TM.rollback();
         }
     }

     @Test
     public void storeLoadLocator() throws Exception {
         // TODO: This test fails on H2 standalone
         // http://groups.google.com/group/h2-database/browse_thread/thread/9c6f4893a62c9b1a
         UserTransaction tx = TM.getUserTransaction();
         try {
             tx.begin();
             EntityManager em = JPA.createEntityManager();

             byte[] bytes = new byte[131072];
             new Random().nextBytes(bytes);
             InputStream imageInputStream = new ByteArrayInputStream(bytes);
             int byteLength = bytes.length;

             Item someItem = new Item();
             someItem.setName("Some item");
             someItem.setDescription("This is some description.");

             // Need the native Hibernate API
             Session session = em.unwrap(Session.class);
             // You need to know the number of bytes you want to read from the stream!
             Blob blob = session.getLobHelper()
                     .createBlob(imageInputStream, byteLength);

             someItem.setImageBlob(blob);
             em.persist(someItem);

             tx.commit();
             em.close();

             Long ITEM_ID = someItem.getId();

             tx.begin();
             em = JPA.createEntityManager();

             Item item = em.find(Item.class, ITEM_ID);

             // You can stream the bytes directly...
             InputStream imageDataStream = item.getImageBlob().getBinaryStream();

             // ... or materialize them into memory:
             ByteArrayOutputStream outStream = new ByteArrayOutputStream();
             StreamUtils.copy(imageDataStream, outStream);
             byte[] imageBytes = outStream.toByteArray();
             assertEquals(imageBytes.length, 131072);

             tx.commit();
             em.close();
         } finally {
             TM.rollback();
         }
     }

 }

 <persistence-unit name="AdvancedPU">
         <jta-data-source>myDS</jta-data-source>
         <class>org.jpwh.model</class>
         <class>org.jpwh.model.advanced.Item</class>
         <class>org.jpwh.model.advanced.Bid</class>
         <class>org.jpwh.model.advanced.User</class>
         <class>org.jpwh.model.advanced.Address</class>
         <class>org.jpwh.model.advanced.City</class>
         <class>org.jpwh.model.advanced.ItemBidSummary</class>
         <exclude-unlisted-classes>true</exclude-unlisted-classes>
         <!--
         <properties>
             <property name="hibernate.hbm2ddl.auto" value="create-drop"/>
         </properties>
         -->
     </persistence-unit>