Question

net.sf.json.JSONException: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: dao.entities.CourseMaster.chapterCourseMappings, no session or session was closed

我的实体：

    @Entity
    @Table(name = "course_master")
    public class CourseMaster implements Serializable {

private Integer id;
private String courseName;
private String category;
private Set<CourseWeightage> courseWeightages = new HashSet<CourseWeightage>();
private Set<ChapterCourseMapping> chapterCourseMappings = new HashSet<ChapterCourseMapping>();

public CourseMaster() {
}

public CourseMaster(String courseName, String category) {
    this.courseName = courseName;
    this.category = category;
}

public CourseMaster(String courseName, String category,
        Set<CourseWeightage> courseWeightages, Set<ChapterCourseMapping> chapterCourseMappings) {
    this.courseName = courseName;
    this.category = category;
    this.courseWeightages = courseWeightages;
    this.chapterCourseMappings = chapterCourseMappings;
}

@Id
@GeneratedValue(strategy = IDENTITY)
@Column(name = "id", unique = true, nullable = false)
public Integer getId() {
    return this.id;
}

public void setId(Integer id) {
    this.id = id;
}

@Column(name = "course_name", nullable = false, length = 100)
public String getCourseName() {
    return this.courseName;
}

public void setCourseName(String courseName) {
    this.courseName = courseName;
}

@Column(name = "category", nullable = false, length = 2)
public String getCategory() {
    return this.category;
}

public void setCategory(String category) {
    this.category = category;
}

@OneToMany(fetch = FetchType.EAGER, mappedBy = "courseMaster")
public Set<CourseWeightage> getCourseWeightages() {
    return this.courseWeightages;
}

public void setCourseWeightages(Set<CourseWeightage> courseWeightages) {
    this.courseWeightages = courseWeightages;
}


@OneToMany(fetch = FetchType.LAZY, mappedBy = "courseMaster")
public Set<ChapterCourseMapping> getChapterCourseMappings() {
    return this.chapterCourseMappings;
}

public void setChapterCourseMappings(Set<ChapterCourseMapping> chapterCourseMappings) {
    this.chapterCourseMappings = chapterCourseMappings;
}
}

控制器方法：（RESTful Web服务API）

导致异常的方法中的潜在操作！

    net.sf.json.JSONObject data = new net.sf.json.JSONObject();

    List<CourseMaster> alrCourseMasters = genericBusiness.getCourses();

    data.put("courselist", alrCourseMasters);

    view = new Viewable("/test.jsp", data);

    return Response.status(200).entity(view).build();

DAO方法：

public List<CourseMaster> getCourses() 
{
    Session session = sessionFactory.openSession();
    Transaction transaction = session.beginTransaction();
    Query query = session.createQuery("from CourseMaster");
    List<CourseMaster> alrCourseMasters = query.list();
    transaction.commit();
    session.flush();
    session.close();
    return alrCourseMasters;
}

Answer 1

如果要将Object序列化为字符串，则应该在关联的hibernate实体中进行初始化。

在你的情况下，

 @OneToMany(fetch = FetchType.LAZY, mappedBy = "courseMaster")
public Set<ChapterCourseMapping> getChapterCourseMappings() {
return this.chapterCourseMappings;
}

重命名为

@OneToMany(fetch = FetchType.EAGER, mappedBy = "courseMaster")
public Set<ChapterCourseMapping> getChapterCourseMappings() {
return this.chapterCourseMappings;
}

同时检查所有关联应该是急切的提取。

或者你可以在hibernate中使用create SQlQueries并将结果映射到某个pojo并将其转换为json字符串。它会起作用。

net.sf.json.JSONException：org.hibernate.LazyInitializationException：懒得初始化角色集合

1 个答案: