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POFind and delete an item from a collection
 

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    <p>I have the following problem with a method of JPA. I can not delete an item from a collection. Actually, the method only works if it is not the last element inserted. Where I'm wrong?</p> <p>This is the class of my model:</p> <pre><code>@Entity public class JobOffer { @SequenceGenerator(name="JobOffer_Gen", sequenceName="JobOffer_Seq", initialValue=1, allocationSize=1) @Id @GeneratedValue(generator="JobOffer_Gen") @Column(name="ID_JOBOFFER") private Long id; @Column private String title; ... @OneToMany @JoinTable(joinColumns = @JoinColumn(name = "JOBOFFER_IDFK"), inverseJoinColumns = @JoinColumn(name = "LANGUAGE_IDFK")) private Collection&lt;Language&gt; languages = new HashSet&lt;Language&gt;(); ... } </code></pre> <p>This is my method in JPA:</p> <pre><code>@Override @Transactional public void deleteLanguage(JobOffer joboffer, Long idLingua) throws BusinessException { for(Language l : joboffer.getLanguages()){ if (l.getId() == idLingua){ joboffer.getLanguages().remove(l); } } em.merge(joboffer); } </code></pre> <p>What is the correct way to search for an item in a collection and delete in JPA?</p> <p>This is the error that I get from the console:</p> <pre><code>21-ott-2013 18.22.27 org.apache.catalina.core.StandardWrapperValve invoke GRAVE: Servlet.service() for servlet [jobbook] in context with path [/jobbook] threw exception [Request processing failed; nested exception is java.util.ConcurrentModificationException] with root cause java.util.ConcurrentModificationException at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372) at java.util.AbstractList$Itr.next(AbstractList.java:343) at org.eclipse.persistence.indirection.IndirectList$1.next(IndirectList.java:571) at it.univaq.mwt.j2ee.jobbook.business.impl.JPAJobOfferService.deleteLanguage(JPAJobOfferService.java:95) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) </code></pre> <p>and then continues</p>
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    1. COAdd an extract of your error trace please.
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    2. COif you iterate over a collection (using an iterator like you do implicit via for(Language l : joboffer.getLanguages()) ), you mustn't modify the collection (what you do via joboffer.getLanguages().remove(l); )
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    3. COmmmmmm... ok...I understand. How can I delete an item from a collection in jpa? How can I make entityManager.find in JobOffer.getLanguages ​​()
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