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>