我读了一个包含大学课程（11000行）的CSV文件，并希望使用hibernate将其插入到MySQL数据库中。问题是hibernate将每行插入两次。有关此问题的错误。解决方案应该是在坚持后冲洗每个孩子。 请参见此处：Hibernate inserts duplicates into a @OneToMany collection和https://hibernate.atlassian.net/browse/HHH-6776 这是我的Spring应用程序控制器的代码：
@RequestMapping(value = "/readcsv")
public String readCSVFile() {
entityManager.setFlushMode(FlushModeType.COMMIT);
//Load all courses and universities and add to hashmap for fast lookup.
ArrayList<Course> allCourses = (ArrayList) entityManager.createQuery("FROM Course").getResultList();
MultiValueMap courseMap = MultiValueMap.decorate(new HashMap<String, Course>());
for (Course c : allCourses) {
courseMap.put(c.getName(), c);
}
ArrayList<University> allUniversities = (ArrayList) entityManager.createQuery("FROM University").getResultList();
HashMap<String, University> universityMap = new HashMap<String, University>();
for (University u : allUniversities) {
universityMap.put(u.getName(), u);
}
Country sweden = (Country) entityManager.createQuery("SELECT c FROM Country c WHERE c.name = 'Sweden'").getSingleResult();
ArrayList<Course> coursesToAdd = new ArrayList<Course>();
//Set fixed parameters for this specific dataset.
String filename = "/Volumes/320gb/macbookpro/Documents/AntagningsstatistikVT2015.csv";
String semester = "Spring2015";
String type = "Classroom";
int pace = 100;
University u;
try {
//Read file
File fileDir = new File(filename);
BufferedReader in = new BufferedReader(new InputStreamReader(new FileInputStream(fileDir), "UTF-8"));
String line;
//Loop lines in file
while ((line = in.readLine()) != null) {
// use comma as separator
String[] courseLine = line.split(",");
String name = courseLine[1];
String university = courseLine[2];
//See if the course is already in the database
Collection<Course> coursesWithSameName = courseMap.getCollection(name);
boolean found = false;
if (coursesWithSameName != null) {
for (Course course: coursesWithSameName) {
if (course.getUniversity().getName().equals(university)) {
System.out.println("COURSE ALREADY IN DB : " + name + " " + university);
found = true;
}
}
}
//If not, insert it
if (found == false) {
if (!universityMap.containsKey(university)) {
u = new University();
u.setName(university);
u.setCountry(sweden);
u.setUserAdded(false);
universityMap.put(u.getName(), u);
entityManager.persist(u);
entityManager.flush();
} else {
u = universityMap.get(university);
}
Course course = new Course();
course.setName(name);
course.setUniversity(u);
course.setType(type);
course.setPace(pace);
course.setSemester(semester);
courseMap.put(course.getName(), course);
coursesToAdd.add(course);
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
System.out.println("NUMBER OF ROWS IN coursesToAdd : " + coursesToAdd.size()); //Correctly prints 11000
for (Course course : coursesToAdd) { //inserts 22000 rows to db.
entityManager.persist(course);
entityManager.flush();
}
return "redirect:/";
}
即使我插入了每个persist个双行后刷新。我在控制器类上有@Transactional注释，这是flush无法解决问题的原因吗？然而，当flush处于import com.courseportal.project.account.Account;
import com.courseportal.project.utils.AbstractTimestampEntity;
import org.hibernate.annotations.Cascade;
import java.io.Serializable;
import java.util.List;
import javax.persistence.*;
@Entity
@Table(name="courses")
public class Course extends AbstractTimestampEntity implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.TABLE)
private long id;
@Column(name = "code")
private String code;
@Column(name = "name")
private String name;
@OneToMany(cascade = CascadeType.ALL)
@OrderBy("date desc")
private List<CourseRank> ranks;
@OneToMany(cascade = CascadeType.ALL)
@OrderBy("date desc")
private List<Comment> comments;
@OneToMany(cascade = CascadeType.ALL)
@OrderBy("date desc")
private List<UserBook> userBooks;
@ElementCollection
private List<CourseBook> courseBooks;
@ManyToMany
@JoinTable(name="courses_enrolledStudents")
private List<Account> enrolledStudents;
@OneToMany(cascade = CascadeType.ALL)
private List<Timeslot> times;
@ManyToOne
private University university;
/*
* fall
* spring
* summer
*/
private String semester;
private String teacherName;
private String courseLink;
private String requirementsLink;
/**
* Undergraduate
* Graduate
*/
private String level;
/**
* Online (MOOC - Massive Open Online Courses)
* Classroom (Traditional)
* Mixed (Lab)
*/
private String type;
/**
* How fast the course going in percentage.
*/
private int pace;
private int numberOfAssignments;
private int numberOfProjects;
private int numberOfExams;
private double credits;
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public University getUniversity() {
return university;
}
public void setUniversity(University university) {
this.university = university;
}
public String getCourseLink() {
return courseLink;
}
public void setCourseLink(String courseLink) {
this.courseLink = courseLink;
}
public String getRequirementsLink() {
return requirementsLink;
}
public void setRequirementsLink(String requirementsLink) {
this.requirementsLink = requirementsLink;
}
public String getLevel() {
return level;
}
public void setLevel(String level) {
this.level = level;
}
public List<Timeslot> getTimes() {
return times;
}
public void setTimes(List<Timeslot> times) {
this.times = times;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public int getPace() {
return pace;
}
public void setPace(int pace) {
this.pace = pace;
}
public String getTeacherName() {
return teacherName;
}
public void setTeacherName(String teacherName) {
this.teacherName = teacherName;
}
public List<Comment> getComments() {
return comments;
}
public void setComments(List<Comment> comments) {
this.comments = comments;
}
public String getCode() {
return code;
}
public void setCode(String code) {
this.code = code;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List<CourseRank> getRanks() {
return ranks;
}
public void setRanks(List<CourseRank> ranks) {
this.ranks = ranks;
}
public void addRank(CourseRank rank) {
this.ranks.add(rank);
}
public void removeRank(CourseRank rank) {
this.ranks.remove(rank);
}
public void addComment(Comment comment) {
comments.add(comment);
}
//User books, books that are for sale getters and setters
public void removeUserBook(UserBook book) {
this.userBooks.remove(book);
}
public void addUserBook(UserBook book) {
this.userBooks.add(book);
}
public List<UserBook> getUserBooks() {
return userBooks;
}
public void setUserBooks(List<UserBook> userBooks) {
this.userBooks = userBooks;
}
public List<CourseBook> getCourseBooks() {
return courseBooks;
}
public void setCourseBooks(List<CourseBook> courseBooks) {
this.courseBooks = courseBooks;
}
public void removeCourseBook(CourseBook book) {
this.courseBooks.remove(book);
}
public void addCourseBook(CourseBook book) {
this.courseBooks.add(book);
}
public int getNumberOfAssignments() {
return numberOfAssignments;
}
public void setNumberOfAssignments(int numberOfassignments) {
this.numberOfAssignments = numberOfassignments;
}
public int getNumberOfProjects() {
return numberOfProjects;
}
public void setNumberOfProjects(int numberOfprojects) {
this.numberOfProjects = numberOfprojects;
}
public int getNumberOfExams() {
return numberOfExams;
}
public void setNumberOfExams(int numberOfexams) {
this.numberOfExams = numberOfexams;
}
public double getCredits() {
return credits;
}
public void setCredits(double credits) {
this.credits = credits;
}
public List<Account> getEnrolledStudents() {
return enrolledStudents;
}
public void setEnrolledStudents(List<Account> enrolledStudents) {
this.enrolledStudents = enrolledStudents;
}
public void addEnrolledStudent(Account student) {
this.enrolledStudents.add(student);
}
public void removeEnrolledStudent(Account student) {
this.enrolledStudents.remove(student);
}
public String getSemester() {
return semester;
}
public void setSemester(String semester) {
this.semester = semester;
}
}
时，它似乎要慢得多，与在末端进行批量插入而不冲洗每个插入物相比，它似乎运行正常。
有人知道我的代码有什么问题吗？
谢谢！
修改
添加了大学和课程实体：
课程：
import com.courseportal.project.utils.AbstractTimestampEntity;
import java.io.Serializable;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.Table;
@Entity
@Table(name="universities")
public class University extends AbstractTimestampEntity implements Serializable {
@Id
@GeneratedValue
private int id;
private String name;
@ManyToOne
private Country country;
private boolean userAdded;
public University() {}
public University(String university) {
name = university;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public Country getCountry() {
return country;
}
public void setCountry(Country country) {
this.country = country;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public boolean isUserAdded() {
return userAdded;
}
public void setUserAdded(boolean userAdded) {
this.userAdded = userAdded;
}
}
大学：
{{1}}