问题是当我尝试保留WordPair并将其链接到词典实体时，hibernate保留新的Dictionary实体，然后保留新的WordPair实体并附加新的词典。如何附加现有的我用form：select项目选择的字典实体？如果我改变
@ManyToOne(fetch = FetchType.EAGER, cascade = javax.persistence.CascadeType.All)
WordPair中的“合并”选项或其他功能
java.lang.IllegalStateException：org.hibernate.TransientPropertyValueException：对象引用了一个未保存的临时实例-在刷新之前保存该临时实例：
我的看法如下：
<form:form modelAttribute="wordpair" action="addWordPair" method="post">
<label for="semanticUnitOne">Enter word one: </label>
<form:input path="semanticUnitOne"/>
<br/>
<label for="semanticUnitTwo">Enter word two: </label>
<form:input path="semanticUnitTwo"/>
<br/>
<div class="form-group">
<label for="dictionary">Dictionary</label>
<form:select path="dictionary" cssClass="selectpicker" items="${dictionaries}" itemLabel="name" itemValue="id">
<%--<form:options items="${dictionaries}" itemValue="id" itemLabel="name"/>--%>
</form:select>
</div>
<input type="submit" class="btn" value="Add word pair"/>
</form:form>
<div class="control-group">
</div>
</div>
控制器如下：
@Controller
public class WordPairController {
@Autowired
WordPairService wordPairService;
@Autowired
DictionaryService dictionaryService;
@RequestMapping(value = "createWordPair", method = RequestMethod.GET)
public String createWordPair(Model model) {
model.addAttribute("wordpair", new WordPair());
model.addAttribute("dictionaries", this.dictionaryService.findAll());
return "addWordPair";
}
@RequestMapping(value = "addWordPair", method = RequestMethod.POST)
public String addWordPair(@ModelAttribute("wordpair") WordPair wordPair, BindingResult result, Dictionary dictionary) {
wordPair.setDictionary(dictionary);
wordPairService.save(wordPair);
return "addWordPair";
}
@RequestMapping(value = "wordPairGet", method = RequestMethod.GET)
public String wordPairGet(Model model) {
model.addAttribute("wordPair", wordPairService.findAllWordPairs());
return "wordPairGet";
}
}
字典的实体如下：
@Entity
public class Dictionary {
@Id
@GeneratedValue
private Long id;
private String name;
private String comment;
@OneToMany(mappedBy = "dictionary", cascade = CascadeType.All, fetch=FetchType.EAGER)
private List<WordPair> wordPairs;
和单词对实体：
@Entity
@Table
public class WordPair {
@Id
@GeneratedValue
private Long id;
private String semanticUnitOne;
private String semanticUnitTwo;
private int rating;
@ManyToOne(fetch = FetchType.EAGER, cascade = javax.persistence.CascadeType.All)
private Dictionary dictionary;
还有一个服务和DAO，
@Repository("dictionaryDao")
public class DictionaryDaoImpl implements DictionaryDao {
@PersistenceContext
private EntityManager em;
public Dictionary save(Dictionary dictionary) {
em.persist(dictionary);
em.flush();
return dictionary;
}
public List<Dictionary> findAllDictionaries() {
List<Dictionary> result = em.createQuery("SELECT d FROM Dictionary d", Dictionary.class).getResultList();
return result;
}
@Repository("wordPairRepository")
public class WordPairDaoImpl implements WordPairDao {
@PersistenceContext
private EntityManager em;
public List<WordPair> findAllWordPairs() {
List<WordPair> result = em.createQuery("SELECT p FROM WordPair p", WordPair.class).getResultList();
return result;
}
public WordPair save(WordPair wordPair) {
em.persist(wordPair);
em.flush();
return wordPair;
}
最佳答案
使用@joinColumn作为Wordpair表ID，在WordPair类中的wordpairId下面
@Entity
@Table
public class WordPair {
@Id
@GeneratedValue
private Long id;
private String semanticUnitOne;
private String semanticUnitTwo;
private int rating;
@ManyToOne(fetch = FetchType.LAZY, cascade =javax.persistence.CascadeType.All)
@JoinColumn(name = "WordPairId")
private Dictionary dictionary;
参见下面的字典类targetEntity作为WordPair.class
@Entity
public class Dictionary {
@Id
@GeneratedValue
private Long id;
private String name;
private String comment;
@OneToMany(mappedBy = "dictionary", cascade = CascadeType.All,fetch=FetchType.LAZY, targetEntity = WordPair.class)
private List<WordPair> wordPairs;