Question

在Customer.java实体类中，我有以下代码：

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

发现当我查询客户实体时，eclipselink生成的SQL没有连接获取CustomerSuppInfo映射（它生成1个SQL来选择customer表，然后另外1个SQL来按id选择supp_info表）我想要的只是生成1个SQL并选择整个客户相关字段，以便最小化SQL生成的/ EJB调用＃。

这两个注释是不是可以共存？我试图找到JPA文档，但似乎没有运气:(

Answer 1

如果注释“@JoinFetch（JoinFetchType.OUTER）”未导致EclipseLink连接为拥有实体上的所有查询提取“suppInfoMap”，并且您没有使用XML覆盖此映射，则这是一个错误。您应该提交EclipseLink错误。或者，您可以使用“JOIN FETCH”JPQL关键字直接创建查询以加入“suppInfoMap”。

Answer 2

您的查询示例

import java.util.HashMap; import java.util.Map;

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

@Entity 公共类部门{ @Id @GeneratedValue（strategy = GenerationType.IDENTITY） private int id; 私有字符串名称; @OneToMany（的mappedBy = “部门”） @MapKey（名称= “名称”）私人地图学生;

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();
}

}

档案：Student.java

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

@Entity 公立班学生{ @Id @GeneratedValue（strategy = GenerationType.IDENTITY） private int id; 私有字符串名称;

@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

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

public class Helper { public static void checkData（）throws Exception { 的Class.forName（ “org.hsqldb.jdbcDriver”）; Connection conn = DriverManager.getConnection（“jdbc：hsqldb：data / tutorial”，“sa”，“”）; Statement 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

import java.util.List;

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

public class Main { static EntityManagerFactory emf = Persistence.createEntityManagerFactory（“JPAService”）; static EntityManager em = emf.createEntityManager（）;

public static void main（String [] a）抛出异常{ em.getTransaction（）开头（）;

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“version =”1.0“＆gt;

Eclipselink @mapkey和@JoinFetch（JoinFetchType.OUTER）不能共存？

2 个答案: