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POMapping a unidirectional OneToMany association on a wrapper object using JPA
 

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    <p>I am converting Hibernate configuration over to using JPA. The current configuration has an AlertPref class (ALERT_PREF table) with a collection of Long types that are primary key values from the ALERT_CATEGORY table. There is an ALERT_PREF_CATEGORY junction table that joins the two. I could setup this relationship in JPA by defining the junction table as an Entity class and having a collection of AlertPrefCategory objects instead of Long IDs in the AlertPref class, but I want to avoid this if possible, and instead setup a uni-directional mapping from AlertPref to the Long IDs. Some of the legacy code uses the IDs, and it would be difficult to change this code.</p> <p>Here's the current class tag in the Hibernate config, which works fine:</p> <pre><code>&lt;class name="AlertPref" table="ALERT_PREF"&gt; &lt;id name="alertPrefId" column="ALERT_PREF_ID" type="long"&gt; &lt;generator class="hilo"&gt; &lt;param name="max_lo"&gt;100&lt;/param&gt; &lt;/generator&gt; &lt;/id&gt; &lt;property name="userId" column="USER_ID" type="string" not-null="true" /&gt; &lt;set name="excludedCategoryIds" table="ALERT_PREF_CATEGORY" cascade="all,delete-orphan"&gt; &lt;key column="ALERT_PREF_ID" /&gt; &lt;element column="EXCLUDED_CATEGORY_ID" type="long" /&gt; &lt;/set&gt; &lt;/class&gt; </code></pre> <p>Here is what I tried to use in JPA, but it is throwing the exception "Use of @OneToMany or @ManyToMany targeting an unmapped class: AlertPref.excludedCategoryIds[java.lang.Long]"</p> <pre><code>@Entity @Table(name = "ALERT_PREF") public class AlertPref { @Id @TableGenerator(name = "table_gen", allocationSize = 1) @GeneratedValue(strategy = GenerationType.TABLE, generator = "table_gen") @Column(name = "ALERT_PREF_ID") private long alertPrefId; @Column(name = "USER_ID", nullable = false) private String userId; @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true) @JoinTable(name = "ALERT_PREF_CATEGORY", joinColumns = @JoinColumn(name = "ALERT_PREF_ID"), inverseJoinColumns = @JoinColumn(name = "EXCLUDED_CATEGORY_ID")) private Set&lt;Long&gt; excludedCategoryIds; /** * @return Returns the alertPrefId. */ public long getAlertPrefId() { return alertPrefId; } /** * @param alertPrefId * The alertPrefId to set. */ public void setAlertPrefId(long alertPrefId) { this.alertPrefId = alertPrefId; } /** * @return Returns the userId. */ public String getUserId() { return userId; } /** * @param userId * The userId to set. */ public void setUserId(String userId) { this.userId = userId; } /** * @return the excludedCategoryIds */ public Set&lt;Long&gt; getExcludedCategoryIds() { return excludedCategoryIds; } /** * @param excludedCategoryIds the excludedCategoryIds to set */ public void setExcludedCategoryIds(Set&lt;Long&gt; excludedCategoryIds) { this.excludedCategoryIds = excludedCategoryIds; } } </code></pre>
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