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Re: Persisting java.util.Map with custom class as key and value
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created by <a href="http://community.jboss.org/people/piotrekde">piotrekde</a> in <i>Beginner's Corner</i> - <a href="http://community.jboss.org/message/601238#601238">View the full discussion</a>
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<div class="jive-rendered-content"><p>Thanks for help!</p><p>I think that the first one option is the easiest one (blob). Can I store object as a blob in a database, but have it defined as a Map type in class properties? What I mean is this (MyEntity class, myBlobMap property):</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><pre class="jive-pre"><code class="jive-code jive-java"> @Local
    <font color="navy"><b>public</b></font> <font color="navy"><b>static</b></font> <font color="navy"><b>interface</b></font> MyEntityRepository <font color="navy">{</font>
        <font color="navy"><b>void</b></font> persist(MyEntity entity);
        MyEntity find(<font color="navy"><b>long</b></font> id);
    <font color="navy">}</font>
 
 
    @Stateful
    <font color="navy"><b>public</b></font> <font color="navy"><b>static</b></font> <font color="navy"><b>class</b></font> MyEntityRepositoryBean <font color="navy"><b>implements</b></font> MyEntityRepository <font color="navy">{</font>
 
 
    @PersistenceContext(unitName = <font color="red">"mydb"</font>)
    <font color="navy"><b>private</b></font> EntityManager entityManager;
 
 
        <font color="navy"><b>public</b></font> <font color="navy"><b>void</b></font> persist(MyEntity entity) <font color="navy">{</font>
            entityManager.persist(entity);
        <font color="navy">}</font>
 
 
        <font color="navy"><b>public</b></font> MyEntity find(<font color="navy"><b>long</b></font> id) <font color="navy">{</font>
            <font color="navy"><b>return</b></font> entityManager.find(MyEntity.class, id);
        <font color="navy">}</font>
    <font color="navy">}</font>
 
 
    @Entity
    @Table(name = <font color="red">"my_entity"</font>)
    <font color="navy"><b>private</b></font> <font color="navy"><b>class</b></font> MyEntity <font color="navy">{</font>
 
 
        @Id
        @GeneratedValue(strategy = GenerationType.AUTO)
        @Column(name = <font color="red">"id"</font>)
        <font color="navy"><b>private</b></font> <font color="navy"><b>long</b></font> id;
 
 
        @Lob
        @Column(name=<font color="red">"my_blob"</font>)
        <font color="navy"><b>private</b></font> Map<CustomClassA, CustomClassB> myBlobMap;
 
 
        <font color="navy"><b>public</b></font> MyEntity() <font color="navy">{</font>
            this.myBlobMap = <font color="navy"><b>new</b></font> LinkedHashMap<CustomClassA, CustomClassB>();
        <font color="navy">}</font>
 
 
        <font color="navy"><b>public</b></font> <font color="navy"><b>long</b></font> getId() <font color="navy">{</font>
            <font color="navy"><b>return</b></font> this.id;
        <font color="navy">}</font>
 
 
        <font color="navy"><b>public</b></font> <font color="navy"><b>void</b></font> putToMap(CustomClassA a, CustomClassB b) <font color="navy">{</font>
            this.myBlobMap.put(a,b);
        <font color="navy">}</font>
 
 
        <font color="navy"><b>public</b></font> Map<CustomClassA, CustomClassB> getMyBlobMap() <font color="navy">{</font>
            <font color="navy"><b>return</b></font> this.myBlobMap;
        <font color="navy">}</font>
    <font color="navy">}</font>
 
 
    <font color="navy"><b>private</b></font> <font color="navy"><b>class</b></font> CustomClassA <font color="navy"><b>implements</b></font> Serializable <font color="navy">{</font>
 
 
        <font color="navy"><b>private</b></font> <font color="navy"><b>double</b></font> a;
        <font color="navy"><b>private</b></font> <font color="navy"><b>double</b></font> b;
 
 
        <font color="navy"><b>public</b></font> CustomClassA(<font color="navy"><b>double</b></font> a, <font color="navy"><b>double</b></font> b) <font color="navy">{</font>
            this.a = a;
            this.b = b;
        <font color="navy">}</font>
 
 
        <font color="navy"><b>public</b></font> <font color="navy"><b>double</b></font> getA() <font color="navy">{</font>
            <font color="navy"><b>return</b></font> this.a;
        <font color="navy">}</font>
 
 
        <font color="navy"><b>public</b></font> <font color="navy"><b>double</b></font> getB() <font color="navy">{</font>
            <font color="navy"><b>return</b></font> this.b;
        <font color="navy">}</font>
    <font color="navy">}</font>
 
 
    <font color="navy"><b>private</b></font> <font color="navy"><b>class</b></font> CustomClassB <font color="navy"><b>implements</b></font> Serializable <font color="navy">{</font>
        <font color="navy"><b>private</b></font> String x;
 
 
        <font color="navy"><b>public</b></font> CustomClassB(String x) <font color="navy">{</font>
            this.x = x;
        <font color="navy">}</font>
 
 
        <font color="navy"><b>public</b></font> String getX() <font color="navy">{</font>
            <font color="navy"><b>return</b></font> this.x;
        <font color="navy">}</font>
    <font color="navy">}</font>
 
</code></pre><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>anyway, if I try to test this code, I'm getting an exception:</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><pre class="jive-pre"><code class="jive-code jive-java"> @Test
    <font color="navy"><b>public</b></font> <font color="navy"><b>void</b></font> testBlobPersistence() <font color="navy"><b>throws</b></font> Exception <font color="navy">{</font>
        MyEntityRepository repo  = (MyEntityRepository) initialContext.lookup(
                <font color="red">"MyEntityRepositoryBeanLocal"</font>);
 
        MyEntity entity = <font color="navy"><b>new</b></font> MyEntity();
        <font color="darkgreen">//entity.putToMap(new CustomClassA(1,2), new CustomClassB("qwertyz"));</font>
        repo.persist(entity);
        MyEntity persisted = repo.find(entity.getId());
 
        <font color="darkgreen">//assertNotNull(persisted.getMyBlobMap());</font>
    <font color="navy">}</font>
 
</code></pre><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><blockquote class="jive-quote"><p>(...)</p><p>Caused by: java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to java.sql.Blob</p><p>(...)</p></blockquote><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Do I have to store it as a blob internally? I found the similar issue here:</p><p><a class="jive-link-external-small" href="http://docs.jboss.org/ejb3/app-server/tutorial/blob/src/org/jboss/tutorial/blob/bean/LobTesterBean.java">http://docs.jboss.org/ejb3/app-server/tutorial/blob/src/org/jboss/tutorial/blob/bean/LobTesterBean.java</a></p><p>( #findBlob:HashMap)</p></div>
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<p style="margin: 0;">Reply to this message by <a href="http://community.jboss.org/message/601238#601238">going to Community</a></p>
<p style="margin: 0;">Start a new discussion in Beginner's Corner at <a href="http://community.jboss.org/choose-container!input.jspa?contentType=1&containerType=14&container=2075">Community</a></p>
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