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POMapping CHAR(0) in MySQL to boolean in Hibernate
 

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  1. POMapping CHAR(0) in MySQL to boolean in Hibernate
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    <p>I have a table named <code>refund_rule</code> in mysql<i>(version 5.5)</i>. Here is it's definition:</p> <pre><code>CREATE TABLE `refund_rule` ( `ID` int(10) unsigned NOT NULL AUTO_INCREMENT, `PERCENTAGE` char(0) DEFAULT NULL COMMENT 'BOOLEAN shortcut.NULL&lt;=&gt;false,EMPTY&lt;=&gt;true', `DEDUCTION_AMOUNT` int(10) unsigned DEFAULT NULL, PRIMARY KEY (`ID`) ); </code></pre> <p>The corresponding class in Hibernate<i>(version 3.2)</i> is named <code>RefundRule</code>. The HBM file looks like this:</p> <pre><code>&lt;?xml version="1.0"?&gt; &lt;!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"&gt; &lt;hibernate-mapping&gt; &lt;class name="hibernatesample.dao.RefundRule" table="refund_rule" catalog="back_end_proc"&gt; &lt;id name="id" type="java.lang.Integer"&gt; &lt;column name="ID" /&gt; &lt;generator class="identity" /&gt; &lt;/id&gt; &lt;property name="percentage" type="string"&gt; &lt;column name="PERCENTAGE" length="0"&gt; &lt;comment&gt;BOOLEAN shortcut.NULL&amp;lt;=&amp;gt;false,EMPTY&amp;lt;=&amp;gt;true&lt;/comment&gt; &lt;/column&gt; &lt;/property&gt; &lt;property name="deductionAmount" type="java.lang.Integer"&gt; &lt;column name="DEDUCTION_AMOUNT" /&gt; &lt;/property&gt; &lt;/class&gt; &lt;/hibernate-mapping&gt; </code></pre> <p>The class generated by the wizard in NetBeans<i>(version 7.0)</i> was this:</p> <pre><code>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; } } </code></pre> <p>I added 2 more methods in it <code>setPercentage(boolean)</code> &amp; <code>isPercentage()</code>, and changed the method <code>setPercentage(String)</code> , so that i can use that <code>String</code> object as <code>boolean</code> in my Java<i>(version 1.6)</i> program.</p> <pre><code>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; } } </code></pre> <p>My Question is:</p> <p>Is there any way that I can keep only two methods: <code>setPercentage(boolean)</code> and <code>isPercentage()</code> , and map the <code>boolean percentage</code> variable to <code>PERCENTAGE CHAR(0)</code> variable in mysql.</p> <p>===================================================================</p> <p><b> EDIT </b> added on <i> 2013-11-23 </i></p> <p>Following the answer by @GreyBeardedGeek , I made following changes in code:</p> <p>(Changes in brief)</p> <ol> <li>Added Class CharToBoolUserType</li> <li>Changed the <code>type</code>-attribute of hbm-element: <i>percentage</i> in RefundRule.hbm.xml</li> </ol> <p>(Code related to above mentioned changes)</p> <ol> <li><p>The class CharToBoolUserType:</p> <pre><code>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; } } </code></pre></li> <li><p>The file RefundRule.hbm.xml:</p> <pre><code>&lt;?xml version="1.0"?&gt; &lt;!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"&gt; &lt;hibernate-mapping&gt; &lt;class name="hibernatesample.dao.RefundRule" table="refund_rule" catalog="back_end_proc"&gt; &lt;id name="id" type="java.lang.Integer"&gt; &lt;column name="ID" /&gt; &lt;generator class="identity" /&gt; &lt;/id&gt; &lt;property name="percentage" type="hibernatesample.dao.CharToBoolUserType"&gt; &lt;column name="PERCENTAGE" length="0"&gt; &lt;comment&gt;BOOLEAN shortcut.NULL&amp;lt;=&amp;gt;false,EMPTY&amp;lt;=&amp;gt;true&lt;/comment&gt; &lt;/column&gt; &lt;/property&gt; &lt;property name="deductionAmount" type="java.lang.Integer"&gt; &lt;column name="DEDUCTION_AMOUNT" /&gt; &lt;/property&gt; &lt;/class&gt; &lt;/hibernate-mapping&gt; </code></pre></li> </ol> <p>Since I want the code of the <code>class CharToBoolUserType</code> to be complete in all sense, I have following questions:<br> 1. What is the class of <code>object</code> in <code>hashCode(Object object)</code>, <code>Boolean</code> or <code>String</code>? Who calls this method?<br> 2. What the method <code>public Object replace(Object original, Object target, Object owner)</code> supposed to do? replace <code>original</code> with <code>target</code> and set/put it in <code>owner</code>. In this case: is <code>original</code> of <code>String</code> type, <code>target</code> of <code>Boolean</code> type, and <code>owner</code> of <code>RefundRule</code> type ?</p> <p>Any suggestion(s) to improve this code is welcome.</p> <p>=================================================</p> <p>Just for reference, the class RefundRule is like this now:</p> <pre><code>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; } } </code></pre>
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