java - 将 MySQL 中的 CHAR(0) 映射到 Hibernate 中的布尔值

Question

我有一个名为refund_rulemysql (version 5.5)的表。这是它的定义：

CREATE TABLE `refund_rule` (
  `ID` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `PERCENTAGE` char(0) DEFAULT NULL COMMENT 'BOOLEAN shortcut.NULL<=>false,EMPTY<=>true',
  `DEDUCTION_AMOUNT` int(10) unsigned DEFAULT NULL,
  PRIMARY KEY (`ID`)
);

Hibernate （3.2 版）中对应的类被命名为RefundRule. HBM 文件如下所示：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="hibernatesample.dao.RefundRule" table="refund_rule" catalog="back_end_proc">
        <id name="id" type="java.lang.Integer">
            <column name="ID" />
            <generator class="identity" />
        </id>
        <property name="percentage" type="string">
            <column name="PERCENTAGE" length="0">
                <comment>BOOLEAN shortcut.NULL&lt;=&gt;false,EMPTY&lt;=&gt;true</comment>
            </column>
        </property>
        <property name="deductionAmount" type="java.lang.Integer">
            <column name="DEDUCTION_AMOUNT" />
        </property>
    </class>
</hibernate-mapping>

NetBeans （7.0 版）中的向导生成的类是这样的：

public class RefundRule  implements java.io.Serializable {

     private Integer id;
     private String percentage;
     private Integer deductionAmount;

    public CancellationRule() {
    }

    public CancellationRule(String percentage, Integer deductionAmount) {
       this.percentage = percentage;
       this.deductionAmount = deductionAmount;
    }

    public Integer getId() {
        return this.id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getPercentage() {
        return this.percentage;
    }

    public void setPercentage(String percentage) {
        this.percentage = percentage;
    }

    public Integer getDeductionAmount() {
        return this.deductionAmount;
    }

    public void setDeductionAmount(Integer deductionAmount) {
        this.deductionAmount = deductionAmount;
    }

}

我在其中添加了另外 2 个方法setPercentage(boolean)& isPercentage()，并更改了方法setPercentage(String)，以便我可以在我的 Java （1.6 版）程序中使用该String对象。boolean

public class RefundRule  implements java.io.Serializable {

    .
    .
    .

    public String getPercentage() {
        return this.percentage;
    }

    public void setPercentage(String percentage) {
        this.percentage = percentage==null?null:"";
    }

    .
    .
    .

    public void setPercentage(boolean percentage){
        setPercentage(percentage?"":null);
    }

    public boolean isPercentage(){
        return percentage!=null;
    }

}

我的问题是：

有什么方法可以让我只保留两种方法：setPercentage(boolean)和，并将变量isPercentage()映射到mysql中的变量。boolean percentagePERCENTAGE CHAR(0)

==================================================== ==================

编辑于2013-11-23添加

根据@GreyBeardedGeek 的回答，我对代码进行了以下更改：

（简要更改）

添加了 CharToBoolUserType 类
更改了RefundRule.hbm.xmltype中 hbm-element: percent 的 -属性

（与上述更改相关的代码）

CharToBoolUserType 类：

import java.io.Serializable;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Types;

import org.hibernate.HibernateException;
import org.hibernate.usertype.UserType;

public class CharToBoolUserType implements UserType {

    private static final int[] SQL_TYPES = {Types.CHAR};

    @Override
    public Object assemble(Serializable serializable, Object object) throws HibernateException {
        return serializable;
    }

    @Override
    public Object deepCopy(Object object) throws HibernateException {
        return object;
    }

    @Override
    public Serializable disassemble(Object value) throws HibernateException {
        return (Serializable) value;
    }

    @Override
    public boolean equals(Object x, Object y) throws HibernateException {
       if (x == y) {
           return true;
       } else if (x == null || y == null) {
           return false;
       } else {
           return x.equals(y);
       }
    }

    @Override
    public boolean isMutable() {
        return false;
    }

    @Override
    public Object nullSafeGet(ResultSet resultSet, String[] names, Object owner) throws HibernateException, SQLException {
        return resultSet.getObject(names[0]) != null;
    }

    @Override
    public void nullSafeSet(PreparedStatement preparedStatement, Object value, int index) throws HibernateException, SQLException {
        preparedStatement.setObject(index, ((Boolean) value).booleanValue() ? "" : null);
    }

    @Override
    public Object replace(Object original, Object target, Object owner) throws HibernateException {
        return original;
    }

    @Override
    public Class returnedClass() {
        return boolean.class;
    }

    @Override
    public int[] sqlTypes() {
        return SQL_TYPES;
    }

    @Override
    public int hashCode(Object object) throws HibernateException {
        if (object == null) {
            return 0;
        }
        // is `object` a String ? Or boolean?
        return 1;
    }
}

文件 RefundRule.hbm.xml：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="hibernatesample.dao.RefundRule" table="refund_rule" catalog="back_end_proc">
        <id name="id" type="java.lang.Integer">
            <column name="ID" />
            <generator class="identity" />
        </id>
        <property name="percentage" type="hibernatesample.dao.CharToBoolUserType">
            <column name="PERCENTAGE" length="0">
                <comment>BOOLEAN shortcut.NULL&lt;=&gt;false,EMPTY&lt;=&gt;true</comment>
            </column>
        </property>
        <property name="deductionAmount" type="java.lang.Integer">
            <column name="DEDUCTION_AMOUNT" />
        </property>
    </class>
</hibernate-mapping>

由于我希望的代码class CharToBoolUserType在所有意义上都是完整的，因此我有以下问题：
1. objectin或的类hashCode(Object object)是什么？谁调用这个方法？ 2. 方法应该怎么做？替换为并设置/放入. 在这种情况下：是类型，类型和类型？BooleanString
public Object replace(Object original, Object target, Object owner)originaltargetowneroriginalStringtargetBooleanownerRefundRule

欢迎任何改进此代码的建议。

=================================================

仅供参考，现在的 RefundRule 类是这样的：

public class RefundRule  implements java.io.Serializable {

     private Integer id;
     private boolean percentage;
     private Integer deductionAmount;

    public RefundRule() {
    }


    public RefundRule(boolean percentage, Integer deductionAmount) {
        this.percentage = percentage;
        this.deductionAmount = deductionAmount;
    }

    public Integer getId() {
        return this.id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public Integer getDeductionAmount() {
        return this.deductionAmount;
    }

    public void setDeductionAmount(Integer deductionAmount) {
        this.deductionAmount = deductionAmount;
    }

    public void setPercentage(boolean percentage){
        this.percentage=percentage;
    }

    public boolean isPercentage(){
        return percentage;
    }

}

score 2 · Accepted Answer

我相信您正在寻找 Hibernate 的 UserType，它允许您提供自定义类型映射。

例如，参见http://docs.jboss.org/hibernate/core/3.6/reference/en-US/html/types.html#types-custom

java - 将 MySQL 中的 CHAR(0) 映射到 Hibernate 中的布尔值

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