Eclipselink @mapkey和@JoinFetch（JoinFetchType.OUTER）無法共存嗎？

Question

在Customer.java實體類中，我有以下代碼：

@OneToMany(cascade = CascadeType.ALL, mappedBy = "customer", fetch = FetchType.EAGER)
@MapKey(name = "key")
@JoinFetch(JoinFetchType.OUTER)
private Map<String, CustomerSuppInfo> suppInfoMap....

找出當我查詢客戶實體時，由eclipselink生成的SQL未加入以獲取CustomerSuppInfo映射（它生成了1個SQL以選擇客戶表，然后生成另外1個SQL以按id選擇supp_info表）所有我想要的是僅生成1條SQL並選擇整個與客戶相關的字段，以便最小化SQL生成的數量/ EJB調用。

這2個注釋不能共存嗎？ 我曾嘗試找到JPA文檔，但似乎沒有運氣:(

Answer 1

如果注釋“ @JoinFetch（JoinFetchType.OUTER）”沒有導致EclipseLink對其擁有的實體上的所有查詢進行聯合，以獲取“ suppInfoMap”，並且您尚未使用XML覆蓋此映射，則這是一個錯誤。 您應該提交EclipseLink錯誤。 或者，您可以使用JPQL關鍵字“ JOIN FETCH”直接創建要加入“ suppInfoMap”的查詢。

Answer 2

查詢示例

導入java.util.HashMap; 導入java.util.Map;

導入javax.persistence.Entity; 導入javax.persistence.GeneratedValue; 導入javax.persistence.GenerationType; 導入javax.persistence.Id; 導入javax.persistence.MapKey; 導入javax.persistence.OneToMany;

@Entity公共類Department {@Id @GeneratedValue（strategy = GenerationType.IDENTITY）private int id; 私有字符串名稱； @OneToMany（mappedBy =“ department”）@MapKey（name =“ name”）私人地圖學生；

public Department() {
    students = new HashMap<String, Student>();
}

public int getId() {
    return id;
}

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

public String getName() {
    return name;
}

public void setName(String deptName) {
    this.name = deptName;
}

public void addStudent(Student student) {
    if (!getStudents().containsKey(student.getName())) {
        getStudents().put(student.getName(), student);
        if (student.getDepartment() != null) {
            student.getDepartment().getStudents().remove(student.getName());
        }
        student.setDepartment(this);
    }
}

public Map<String,Student> getStudents() {
    return students;
}

public String toString() {
    return "Department id: " + getId() + 
           ", name: " + getName();
}

}

檔案：Student.java

導入javax.persistence.Entity; 導入javax.persistence.GeneratedValue; 導入javax.persistence.GenerationType; 導入javax.persistence.Id; 導入javax.persistence.ManyToOne;

@Entity公共類Student {@Id @GeneratedValue（strategy = GenerationType.IDENTITY）private int id; 私有字符串名稱；

@ManyToOne
private Department department;

public int getId() {
    return id;
}

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

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}


public Department getDepartment() {
    return department;
}

public void setDepartment(Department department) {
    this.department = department;
}

public String toString() {
    return "Student id: " + getId() + " name: " + getName() + 
           " with " + getDepartment();
}

}

文件：Helper.java

導入java.sql.Connection; 導入java.sql.DriverManager; 導入java.sql.ResultSet; 導入java.sql.ResultSetMetaData; 導入java.sql.Statement;

公共類Helper {公共靜態void checkData（）引發異常{Class.forName（“ org.hsqldb.jdbcDriver”）; 連接conn = DriverManager.getConnection（“ jdbc：hsqldb：data / tutorial”，“ sa”，“”）; 語句st = conn.createStatement（）;

ResultSet mrs = conn.getMetaData().getTables(null, null, null, new String[] { "TABLE" });
while (mrs.next()) {
  String tableName = mrs.getString(3);
  System.out.println("\n\n\n\nTable Name: "+ tableName);

  ResultSet rs = st.executeQuery("select * from " + tableName);
  ResultSetMetaData metadata = rs.getMetaData();
  while (rs.next()) {
    System.out.println(" Row:");
    for (int i = 0; i < metadata.getColumnCount(); i++) {
      System.out.println("    Column Name: "+ metadata.getColumnLabel(i + 1)+ ",  ");
      System.out.println("    Column Type: "+ metadata.getColumnTypeName(i + 1)+ ":  ");
      Object value = rs.getObject(i + 1);
      System.out.println("    Column Value: "+value+"\n");
    }
  }
}

}}

文件：Main.java

導入java.util.List;

導入javax.persistence.EntityManager; 導入javax.persistence.EntityManagerFactory; 導入javax.persistence.Persistence; 導入javax.persistence.Query;

公共類Main {靜態EntityManagerFactory emf = Persistence.createEntityManagerFactory（“ JPAService”）; 靜態EntityManager em = emf.createEntityManager（）;

公共靜態void main（String [] a）引發異常{em.getTransaction（）。begin（）;

Student student = new Student();
student.setName("Joe");
em.persist(student);

Department dept = new Department();
dept.addStudent(student);
em.persist(dept);

em.flush();






Query query = em.createQuery("SELECT e FROM Student e");
List<Student> list = (List<Student>) query.getResultList();
System.out.println(list);

query = em.createQuery("SELECT d FROM Department d");
List<Department> dList = (List<Department>) query.getResultList();
System.out.println(dList);

em.getTransaction().commit();
em.close();
emf.close();

Helper.checkData();

}}

文件：persistence.xml

http://java.sun.com/xml/ns/persistence/persistence“版本=” 1.0“>