JavaPersistenceWithHibernate第二版笔记-第五章-Mapping value types-007UserTypes的用法(@org.hibernate.annotations.Type、@org.hibernate.annotations.TypeDefs、CompositeUserType、DynamicParameterizedType、、、)

一、结构

二、Hibernate支持的UserTypes接口

 UserType —You can transform values by interacting with the plain JDBC PreparedStatement (when storing data) and ResultSet (when loading data).By implementing this interface, you can also control how Hibernate caches and
dirty-checks values. The adapter for MonetaryAmount has to implement this interface.
 CompositeUserType —This extends UserType , providing Hibernate with more details about your adapted class. You can tell Hibernate that the MonetaryAmount component has two properties: amount and currency . You can then reference these properties in queries with dot notation: for example, select avg(i.buyNowPrice.amount) from Item i .
 ParameterizedUserType —This provides settings to your adapter in mappings.You have to implement this interface for the MonetaryAmount conversion,because in some mappings you want to convert the amount to US dollars and in
other mappings to Euros. You only have to write a single adapter and can customize its behavior when mapping a property.
 DynamicParameterizedType —This more powerful settings API gives you access to dynamic information in the adapter, such as the mapped column and table names. You might as well use this instead of ParameterizedUserType ; there is no additional cost or complexity.
 EnhancedUserType —This is an optional interface for adapters of identifier properties and discriminators. Unlike JPA converters, a UserType in Hibernate can be an adapter for any kind of entity property. Because MonetaryAmount won’t be the type of an identifier property or discriminator, you won’t need it.
 UserVersionType —This is an optional interface for adapters of version properties.
 UserCollectionType —This rarely needed interface is used to implement custom collections. You have to implement it to persist a non- JDK collection and preserve additional semantics.

三、代码

1.

package org.jpwh.converter;

import org.hibernate.engine.spi.SessionImplementor;
import org.hibernate.type.StandardBasicTypes;
import org.hibernate.type.Type;
import org.hibernate.usertype.CompositeUserType;
import org.hibernate.usertype.DynamicParameterizedType;
import org.jpwh.model.advanced.MonetaryAmount;

import java.io.Serializable;
import java.lang.annotation.Annotation;
import java.math.BigDecimal;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Currency;
import java.util.Properties;

public class MonetaryAmountUserType
    implements CompositeUserType, DynamicParameterizedType {

    protected Currency convertTo;

    public void setParameterValues(Properties parameters) {

        /**
         * You can access some dynamic parameters here, such as the
         * name of the mapped columns, the mapped (entity) table, or even the
         * annotations on the field/getter of the mapped property. We won't need
         * them in this example though.
         */
        ParameterType parameterType =
            (ParameterType) parameters.get(PARAMETER_TYPE);
        String[] columns = parameterType.getColumns();
        String table = parameterType.getTable();
        Annotation[] annotations = parameterType.getAnnotationsMethod();

        /**
         * We only use the <code>convertTo</code> parameter to
         * determine the target currency when saving a value into the database.
         * If the parameter hasn't been set, we default to US Dollar.
         */
        String convertToParameter = parameters.getProperty("convertTo");
        this.convertTo = Currency.getInstance(
            convertToParameter != null ? convertToParameter : "USD"
        );
    }

    /**
     * The method <code>returnedClass</code> adapts the given class, in this case
     * <code>MonetaryAmount</code>.
     */
    public Class returnedClass() {
        return MonetaryAmount.class;
    }

    /**
     * Hibernate can enable some optimizations if it knows
     * that <code>MonetaryAmount</code> is immutable.
     */
    public boolean isMutable() {
        return false;
    }

    /**
     * If Hibernate has to make a copy of the value, it will call
     * this method. For simple immutable classes like <code>MonetaryAmount</code>,
     * you can return the given instance.
     */
    public Object deepCopy(Object value) {
        return value;
    }

    /**
     * Hibernate calls <code>disassemble</code> when it stores a value in the global shared second-level
     * cache. You need to return a <code>Serializable</code> representation. For <code>MonetaryAmount</code>,
     * a <code>String</code> representation is an easy solution. Or, because <code>MonetaryAmount</code> is actually
     * <code>Serializable</code>, you could return it directly.
     */
    public Serializable disassemble(Object value,
                                    SessionImplementor session) {
        return value.toString();
    }

    /**
     * Hibernate calls this method when it reads the serialized
     * representation from the global shared second-level cache. We create a
     * <code>MonetaryAmount</code> instance from the <code>String</code>
     * representation. Or, if have stored a serialized <code>MonetaryAmount</code>,
     * you could return it directly.
     */
    public Object assemble(Serializable cached,
                           SessionImplementor session, Object owner) {
        return MonetaryAmount.fromString((String) cached);
    }

    /**
     * Called during <code>EntityManager#merge()</code> operations, you
     * need to return a copy of the <code>original</code>. Or, if your value type is
     * immutable, like <code>MonetaryAmount</code>, you can simply return the original.
     */
    public Object replace(Object original, Object target,
                          SessionImplementor session, Object owner) {
        return original;
    }

    /**
     * Hibernate will use value equality to determine whether the value
     * was changed, and the database needs to be updated. We rely on the equality
     * routine we have already written on the <code>MonetaryAmount</code> class.
     */
    public boolean equals(Object x, Object y) {
        return x == y || !(x == null || y == null) && x.equals(y);
    }

    public int hashCode(Object x) {
        return x.hashCode();
    }

    /**
     * Called to read the <code>ResultSet</code>, when a
     * <code>MonetaryAmount</code> value has to be retrieved from the database.
     * We take the <code>amount</code> and <code>currency</code> values as given
     * in the query result, and create a new instance of <code>MonetaryAmount</code>.
     */
    public Object nullSafeGet(ResultSet resultSet,
                              String[] names,
                              SessionImplementor session,
                              Object owner) throws SQLException {

        BigDecimal amount = resultSet.getBigDecimal(names[0]);
        if (resultSet.wasNull())
            return null;
        Currency currency =
            Currency.getInstance(resultSet.getString(names[1]));
        return new MonetaryAmount(amount, currency);
    }

    /**
     * Called when a <code>MonetaryAmount</code> value has
     * to be stored in the database. We convert the value to the target currency,
     * then set the <code>amount</code> and <code>currency</code> on the
     * provided <code>PreparedStatement</code>. (Unless the <code>MonetaryAmount</code>
     * was <code>null</code>, in that case, we call <code>setNull()</code> to
     * prepare the statement.)
     */
    public void nullSafeSet(PreparedStatement statement,
                            Object value,
                            int index,
                            SessionImplementor session) throws SQLException {

        if (value == null) {
            statement.setNull(
                index,
                StandardBasicTypes.BIG_DECIMAL.sqlType());
            statement.setNull(
                index + 1,
                StandardBasicTypes.CURRENCY.sqlType());
        } else {
            MonetaryAmount amount = (MonetaryAmount) value;
            // When saving, convert to target currency
            MonetaryAmount dbAmount = convert(amount, convertTo);
            statement.setBigDecimal(index, dbAmount.getValue());
            statement.setString(index + 1, convertTo.getCurrencyCode());
        }
    }

    /**
     * Here you can implement whatever currency conversion routine
     * you need. For the sake of the example, we simply double the value so we
     * can easily test if conversion was successful. You'll have to replace this
     * code with a real currency converter in a real application. It's not a
     * method of the Hibernate <code>UserType</code> API.
     */
    protected MonetaryAmount convert(MonetaryAmount amount,
                                     Currency toCurrency) {
        return new MonetaryAmount(
            amount.getValue().multiply(new BigDecimal(2)),
            toCurrency
        );
    }

    public String[] getPropertyNames() {
        return new String[]{"value", "currency"};
    }

    public Type[] getPropertyTypes() {
        return new Type[]{
            StandardBasicTypes.BIG_DECIMAL,
            StandardBasicTypes.CURRENCY
        };
    }

    public Object getPropertyValue(Object component,
                                   int property) {
        MonetaryAmount monetaryAmount = (MonetaryAmount) component;
        if (property == 0)
            return monetaryAmount.getValue();
        else
            return monetaryAmount.getCurrency();
    }

    public void setPropertyValue(Object component,
                                 int property,
                                 Object value) {
        throw new UnsupportedOperationException(
            "MonetaryAmount is immutable"
        );
    }

    // ...
}

2.

@org.hibernate.annotations.TypeDefs({
    @org.hibernate.annotations.TypeDef(
        name = "monetary_amount_usd",
        typeClass = MonetaryAmountUserType.class,
        parameters = {@Parameter(name = "convertTo", value = "USD")}
    ),
    @org.hibernate.annotations.TypeDef(
        name = "monetary_amount_eur",
        typeClass = MonetaryAmountUserType.class,
        parameters = {@Parameter(name = "convertTo", value = "EUR")}
    )
})
package org.jpwh.converter;

import org.hibernate.annotations.Parameter;

3.

package org.jpwh.model.advanced.usertype;

import org.jpwh.model.advanced.MonetaryAmount;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.validation.constraints.NotNull;

@Entity
public class Item {

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

    @NotNull
    protected String name;

    @NotNull
    @org.hibernate.annotations.Type(
        type = "monetary_amount_usd"
    )
    @org.hibernate.annotations.Columns(columns = {
        @Column(name = "BUYNOWPRICE_AMOUNT"),
        @Column(name = "BUYNOWPRICE_CURRENCY", length = 3)
    })
    protected MonetaryAmount buyNowPrice;

    @NotNull
    @org.hibernate.annotations.Type(
        type = "monetary_amount_eur"
    )
    @org.hibernate.annotations.Columns(columns = {
        @Column(name = "INITIALPRICE_AMOUNT"),
        @Column(name = "INITIALPRICE_CURRENCY", length = 3)
    })
    protected MonetaryAmount initialPrice;

    public Long getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public MonetaryAmount getBuyNowPrice() {
        return buyNowPrice;
    }

    public void setBuyNowPrice(MonetaryAmount buyNowPrice) {
        this.buyNowPrice = buyNowPrice;
    }

    public MonetaryAmount getInitialPrice() {
        return initialPrice;
    }

    public void setInitialPrice(MonetaryAmount initialPrice) {
        this.initialPrice = initialPrice;
    }

    // ...
}

4.

package org.jpwh.model.advanced;

import java.io.Serializable;
import java.math.BigDecimal;
import java.util.Currency;

/* 
   This value-typed class should be <code>java.io.Serializable</code>: When Hibernate stores entity
   instance data in the shared second-level cache (see <a href="#Caching"/>), it <em>disassembles</em>
   the entity's state. If an entity has a <code>MonetaryAmount</code> property, the serialized
   representation of the property value will be stored in the second-level cache region. When entity
   data is retrieved from the cache region, the property value will be deserialized and reassembled.
 */
public class MonetaryAmount implements Serializable {

    /*
 The class does not need a special constructor, you can make it immutable, even with
        <code>final</code> fields, as your code will be the only place an instance is created.
     */
    protected final BigDecimal value;
    protected final Currency currency;

    public MonetaryAmount(BigDecimal value, Currency currency) {
        this.value = value;
        this.currency = currency;
    }

    public BigDecimal getValue() {
        return value;
    }

    public Currency getCurrency() {
        return currency;
    }

    /*
 You should implement the <code>equals()</code> and <code>hashCode()</code>
        methods, and compare monetary amounts "by value".
     */
    public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof MonetaryAmount)) return false;

        final MonetaryAmount monetaryAmount = (MonetaryAmount) o;

        if (!value.equals(monetaryAmount.value)) return false;
        if (!currency.equals(monetaryAmount.currency)) return false;

        return true;
    }

    public int hashCode() {
        int result;
        result = value.hashCode();
        result = 29 * result + currency.hashCode();
        return result;
    }

    /*
 You will need a <code>String</code> representation of a monetary
        amount. Implement the <code>toString()</code> method and a static method to
        create an instance from a <code>String</code>.
     */
    public String toString() {
        return getValue() + " " + getCurrency();
    }

    public static MonetaryAmount fromString(String s) {
        String[] split = s.split(" ");
        return new MonetaryAmount(
            new BigDecimal(split[0]),
            Currency.getInstance(split[1])
        );
    }
}

5.