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我尝试使用hibernate java框架持久化具有AtomicInteger变量而不是Integer的对象(保存后我需要在线程安全场景中使用该对象)但是当我尝试保存我的对象时java抛出:

java.lang.ClassCastException: java.util.concurrent.atomic.AtomicInteger cannot be cast to java.lang.Integer

有没有办法将 AtomicInteger 映射到整数?有一个对象的例子:

public class Statistics implements java.io.Serializable {
  private AtomicInteger id;
  private AtomicInteger totalErrors;

  public Statistics() {
  }


  public AtomicInteger getTotalErrors() {
    return this.totalErrors;
  }

  public void seTotalErrors(AtomicInteger totalErrors) {
    this.totalErrors= totalErrors;
  }
}

以及相应的 POJO xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
   <class name="Statistics" table="statistics" catalog="example" optimistic-lock="version">
      <id name="id" type="java.lang.Integer">
         <column name="id" />
         <generator class="identity" />
      </id>
      <property name="totalErrors" type="java.lang.Integer">
         <column name="total_errors" />
      </property>
   </class>
</hibernate-mapping>

还有休眠版本:

    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>5.2.10.Final</version>
    </dependency>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-hikaricp</artifactId>
        <version>5.2.10.Final</version>
    </dependency>
4

2 回答 2

3

一种方法是编写一个 JPA 2.1 AttributeConverter,将 Integer 转换为 AtomicInteger,如下所示

@Converter
public class AtomicIntConverter implements AttributeConverter<AtomicInteger, Integer> {


 @Override
 public Integer convertToDatabaseColumn(AtomicInteger attribute) {
  return attribute.get();
 }

 @Override
 public AtomicInteger convertToEntityAttribute(Integer dbData) {
  return new AtomicInteger(dbData);
 }

}

通常,您可以在类字段@Convert上使用 JPA 注释,如下所示:@Entity

@Convert(converter = AtomicIntConverter.class)
private AtomicInteger totalErrors;

您可以在此处的 Hibernate 5.2 文档中阅读有关它的更多信息。

但是当您使用的是休眠映射文件时,请确保将 Converter 类的 FQN 设置为字段的类型,而不是使用@Converter注解。

<property name="totalErrors" type="fully.qualified.name.of.AtomicIntConverter">
     <column name="total_errors" />
 </property>
于 2017-09-12T11:04:35.223 回答
0

最后更好的解决方案(因为更标准的休眠转换器https://docs.jboss.org/hibernate/orm/4.2/manual/en-US/html/ch06.html)是创建一个休眠用户类型类。我不知道是什么原因,因为 AttributeConverter 不起作用(因为它在 hibernate 文档中)。

这适用于我的 Hibernate 5.2。创建一个实现休眠用户类型的 AtomicIntegerType:

import java.io.Serializable;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.logging.Logger;
import org.hibernate.HibernateException;
import org.hibernate.engine.spi.SharedSessionContractImplementor;
import org.hibernate.usertype.UserType;

public class AtomicIntegerType implements UserType {

    private static final Logger logger = Logger.getLogger("AtomicInteger");

    /**
     * Returns the object from the 2 level cache
     */
    @Override
    public Object assemble(final Serializable cached, final Object owner)
            throws HibernateException {
        //would work as the AtomicInteger.class is Serializable, 
        //and stored in cache as it is - see disassemble
        return cached;
    }

    /**
     * Used to create Snapshots of the object
     */
    @Override
    public Object deepCopy(Object value) throws HibernateException {
        //return value; -> if AtomicInteger.class was immutable we could return the object as it is
        final AtomicInteger recievedParam = (AtomicInteger) value;
        final AtomicInteger atomicInteger = new AtomicInteger(recievedParam.get());
        return atomicInteger;
    }

    /**
     * method called when Hibernate puts the data in a second level cache. The
     * data is stored in a serializable form
     */
    @Override
    public Serializable disassemble(final Object value) throws HibernateException {
        //For this purpose the AtomicInteger.class must implement serializable
        return (Serializable) value;
    }

    /**
     * Used while dirty checking - control passed on to the
     * {@link AtomicInteger}
     */
    @Override
    public boolean equals(final Object o1, final Object o2) throws HibernateException {
        boolean isEqual = false;
        if (o1 == o2) {
            isEqual = true;
        }
        if (null == o1 || null == o2) {
            isEqual = false;
        } else {
            isEqual = o1.equals(o2);
        }
        return isEqual;
        //for this to work correctly the equals() 
        //method must be implemented correctly by AtomicInteger class
    }

    @Override
    public int hashCode(final Object value) throws HibernateException {
        return value.hashCode();
        //for this to work correctly the hashCode() 
        //method must be implemented correctly by AtomicInteger class

    }

    /**
     * Helps hibernate apply certain optimizations for immutable objects
     */
    @Override
    public boolean isMutable() {
        return true; //The audit fields can be modified
    }

    /**
     * This method retrieves the property value from the JDBC resultSet
     */
    @Override
    public Object nullSafeGet(ResultSet resultSet, String[] names, SharedSessionContractImplementor ssci, Object owner) throws HibernateException, SQLException {
        //owner here is class from where the call to retrieve data was made.
        //In this case the Test class
        AtomicInteger atomicInteger = null;
        if (!resultSet.wasNull()) {
            atomicInteger = new AtomicInteger(resultSet.getInt(names[0]));            
        }
        return atomicInteger;
    }

    /**
     * The method writes the property value to the JDBC prepared Statement
     *
     */
    @Override
    public void nullSafeSet(final PreparedStatement statement,
            final Object value, final int index, SharedSessionContractImplementor ssci) throws HibernateException,
            SQLException {
        if (null == value) {
            statement.setNull(index, java.sql.Types.INTEGER);
        } else {
            AtomicInteger atomicInteger = (AtomicInteger) value;
            if (null != atomicInteger) {
                statement.setInt(index , atomicInteger.get());
            } else {
                statement.setNull(index, java.sql.Types.INTEGER);
            }

        }
    }

    /**
     * Method used by Hibernate to handle merging of detached object.
     */
    @Override
    public Object replace(final Object original, final Object target,
            final Object owner)
            throws HibernateException {
        //return original; // if immutable use this
        //For mutable types at bare minimum return a deep copy of first argument
        return this.deepCopy(original);

    }

    /**
     * Method tells Hibernate which Java class is mapped to this Hibernate Type
     */
    @SuppressWarnings("rawtypes")
    @Override
    public Class returnedClass() {
        return AtomicInteger.class;
    }

    /**
     * Method tells Hibernate what SQL columns to use for DDL schema generation.
     * using the Hibernate Types leaves Hibernate free to choose actual SQl
     * types based on database dialect. (Alternatively SQL types can also be
     * used directly)
     */
    @Override
    public int[] sqlTypes() {
        //createdBy, createdDate,modifiedBy,modifiedDate
        return new int[]{java.sql.Types.INTEGER};
    }

}

并在休眠映射文件中将 Integer 更改为 AtomicIntegerType ,如下所示:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<!-- Generated 12-sep-2017 13:14:50 by Hibernate Tools 4.3.1 -->
<hibernate-mapping>
   <class name="classs.location.Statistics" table="statistics" catalog="CATALOG" optimistic-lock="version">
      <id name="id" type="java.lang.Integer">
         <column name="id" />
         <generator class="identity" />
      </id>
      <property name="totalErrors" type="class.location.AtomicIntegerType">
         <column name="total_errors" />
      </property>
   </class>
</hibernate-mapping>
于 2017-09-18T11:16:49.760 回答