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我在mysql （version 5.5）中有一個名爲refund_rule的表。下面是它的定義：將MySQL中的CHAR（0）映射到休眠中的布爾值
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`)
);
在Hibernate中對應的類（3.2版）名爲RefundRule。 HBM的文件看起來像這樣：
<?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<=>false,EMPTY<=>true</comment>
</column>
</property>
<property name="deductionAmount" type="java.lang.Integer">
<column name="DEDUCTION_AMOUNT" />
</property>
</class>
</hibernate-mapping>
通過在NetBeans 嚮導生成的類（版本7.0）是這樣的：
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;
}
}
我加入2-多種方法在它setPercentage(boolean) & isPercentage()，和改變了方法setPercentage(String)，以便我可以在我的Java （版本1.6）程序中使用該String對象作爲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;
}
}
我的問題是：
有什麼辦法，我可以只保留兩個方法：setPercentage(boolean)和isPercentage()，並映射在MySQL中boolean percentage變量PERCENTAGE CHAR(0)變量。
==============================================加入=====================
編輯上 2013年11月23日
繼@GreyBeardedGeek答案，我做了以下代碼中的變化：
（變化簡短）
- 添加的類CharToBoolUserTy PE
- 改變了
type-attribute HBM-元件的：百分比在RefundRule.hbm.xml
（代碼與上述的變化）
類CharToBoolUserType：
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; } }該文件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<=>false,EMPTY<=>true</comment> </column> </property> <property name="deductionAmount" type="java.lang.Integer"> <column name="DEDUCTION_AMOUNT" /> </property> </class> </hibernate-mapping>
因爲我想class CharToBoolUserType的代碼來完成所有的意義，我有以下問題：
1.什麼是hashCode(Object object)，Boolean或String類的object？誰稱這種方法？
2.方法public Object replace(Object original, Object target, Object owner)應該做什麼？用target替換original並將其設置/放入owner。在這種情況下：original的String類型，target的Boolean類型和owner的RefundRule類型？
任何建議，以改善此代碼是值得歡迎的。
============================================== ===
僅供參考，類RefundRule是現在這個樣子：
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;
}
}