JavaPersistenceWithHibernate第二版笔记-第四章-Mapping persistent classes-003映射实体时的可选操作(<delimited-identifiers/>、PhysicalNamingStrategy、PhysicalNamingStrategyStandardImpl、、、)

一、自定义映射的表名

1.

 @Entity
 @Table(name = "USERS")
 public class User implements Serializable {
     // ...
 }

2.用定界符

 //@Table(name = "`USER`")的标准
 @Table(name = "`USER`")

 //JPA的标准
 @Table(name = "\"USER\"")

若全部SQL都加定界符, create an orm.xml file and add the setting <delimited-identifiers/> to its <persistence-unit-defaults> section，Hibernate then enforces quoted identifiers everywhere.

3.若要映射的表都有前缀，则可用实现PhysicalNamingStrategy接口或继承已有的实现

 package org.jpwh.shared;

 import org.hibernate.boot.model.naming.Identifier;
 import org.hibernate.engine.jdbc.env.spi.JdbcEnvironment;

 /**
  * Prefixes all SQL table names with "CE_", for CaveatEmptor.
  */
 public class CENamingStrategy extends
     org.hibernate.boot.model.naming.PhysicalNamingStrategyStandardImpl {

     @Override
     public Identifier toPhysicalTableName(Identifier name,
                                           JdbcEnvironment context) {
         return new Identifier("CE_" + name.getText(), name.isQuoted());
     }

 }

You have to enable the naming-strategy implementation in persistence.xml:

 <persistence-unit>name="CaveatEmptorPU">
     ...
     <properties>
         <property name="hibernate.physical_naming_strategy" value="org.jpwh.shared.CENamingStrategy" />
     </properties>
 </persistence-unit>

4.用ImplicitNamingStrategy

二、自定义实体名

1.

 package my.other.model;
 @javax.persistence.Entity(name = "AuctionItem")
 public class Item {
     // ...
 }

三、动态生成SQL

To disable generation of INSERT and UPDATE SQL statements on startup, you need native Hibernate annotations:

 @Entity
 @org.hibernate.annotations.DynamicInsert
 @org.hibernate.annotations.DynamicUpdate
 public class Item {
     // ...
 }

四、实体相关选项

1.Making an entity immutable

 @Entity
 @org.hibernate.annotations.Immutable
 public class Bid {
     // ...
 }

2.Mapping an entity to a subselect

When an instance of ItemBidSummary is loaded, Hibernate executes your custom SQL
SELECT as a subselect:

Synchronize注解的作用：Hibernate will then know it has to flush modifications of Item and Bid instances
before it executes a query against ItemBidSummary

 package org.jpwh.model.advanced;

 import javax.persistence.Entity;
 import javax.persistence.Id;

 @Entity
 @org.hibernate.annotations.Immutable
 @org.hibernate.annotations.Subselect(
     value = "select i.ID as ITEMID, i.ITEM_NAME as NAME, " +
             "count(b.ID) as NUMBEROFBIDS " +
             "from ITEM i left outer join BID b on i.ID = b.ITEM_ID " +
             "group by i.ID, i.ITEM_NAME"
 )

 // TODO Table names are case sensitive, Hibernate bug HHH-8430
 @org.hibernate.annotations.Synchronize({"Item", "Bid"})
 public class ItemBidSummary {

     @Id
     protected Long itemId;

     protected String name;

     protected long numberOfBids;

     public ItemBidSummary() {
     }

     // Getter methods...
     public Long getItemId() {
         return itemId;
     }

     public String getName() {
         return name;
     }

     public long getNumberOfBids() {
         return numberOfBids;
     }

     // ...
 }

五、测试代码

1.

 package org.jpwh.test.advanced;

 import org.jpwh.env.JPATest;
 import org.jpwh.model.advanced.Bid;
 import org.jpwh.model.advanced.Item;
 import org.jpwh.model.advanced.ItemBidSummary;
 import org.testng.annotations.Test;

 import javax.persistence.EntityManager;
 import javax.persistence.Query;
 import javax.transaction.UserTransaction;
 import java.math.BigDecimal;

 import static org.testng.Assert.assertEquals;

 public class MappedSubselect extends JPATest {

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

     @Test
     public void loadSubselectEntity() throws Exception {
         long ITEM_ID = storeItemAndBids();

         UserTransaction tx = TM.getUserTransaction();
         try {
             tx.begin();
             EntityManager em = JPA.createEntityManager();

             {
                 ItemBidSummary itemBidSummary = em.find(ItemBidSummary.class, ITEM_ID);
                 // select * from (
                 //      select i.ID as ITEMID, i.ITEM_NAME as NAME, ...
                 // ) where ITEMID = ?

                 assertEquals(itemBidSummary.getName(), "AUCTION: Some item");
             }
             em.clear();

             { // Hibernate will synchronize the right tables before querying
                 Item item = em.find(Item.class, ITEM_ID);
                 item.setName("New name");

                 // No flush before retrieval by identifier!
                  //ItemBidSummary itemBidSummary = em.find(ItemBidSummary.class, ITEM_ID);

                 // Automatic flush before queries if synchronized tables are affected!
                 Query query = em.createQuery(
                     "select ibs from ItemBidSummary ibs where ibs.itemId = :id"
                 );
                 ItemBidSummary itemBidSummary =
                     (ItemBidSummary)query.setParameter("id", ITEM_ID).getSingleResult();

                 assertEquals(itemBidSummary.getName(), "AUCTION: New name");
             }

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

     public Long storeItemAndBids() throws Exception {
         UserTransaction tx = TM.getUserTransaction();
         tx.begin();
         EntityManager em = JPA.createEntityManager();
         Item item = new Item();
         item.setName("Some item");
         item.setDescription("This is some description.");
         em.persist(item);
         for (int i = 1; i <= 3; i++) {
             Bid bid = new Bid();
             bid.setAmount(new BigDecimal(10 + i));
             bid.setItem(item);
             em.persist(bid);
         }
         tx.commit();
         em.close();
         return item.getId();
     }

 }

Note that Hibernate doesn’t flush automatically before a find() operation—only before a Query is executed, if necessary. Hibernate detects that the modified Item will affect the result of the query, because the ITEM table is synchronized with ItemBid-Summary . Hence, a flush and the UPDATE of the ITEM row are necessary to avoid the

query returning stale data.

2.

 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;
     }
 }

3.

 package org.jpwh.model.advanced;

 import org.jpwh.model.Constants;

 import javax.persistence.Entity;
 import javax.persistence.FetchType;
 import javax.persistence.GeneratedValue;
 import javax.persistence.Id;
 import javax.persistence.JoinColumn;
 import javax.persistence.ManyToOne;
 import javax.validation.constraints.NotNull;
 import java.math.BigDecimal;

 @Entity
 @org.hibernate.annotations.Immutable
 public class Bid {

     @Id
     @GeneratedValue(generator = Constants.ID_GENERATOR)
     protected Long id;

     @NotNull
     protected BigDecimal amount;

     @ManyToOne(optional = false, fetch = FetchType.LAZY) // NOT NULL
     @JoinColumn(name = "ITEM_ID") // Actually the default name
     protected Item item;

     public Long getId() {
         return id;
     }

     public BigDecimal getAmount() {
         return amount;
     }

     public void setAmount(BigDecimal amount) {
         this.amount = amount;
     }

     public Item getItem() {
         return item;
     }

     public void setItem(Item item) {
         this.item = item;
     }
 }