java – 数据库设计,不传递jdbc

我有一个数据库设计问题,我面临着我的一个项目.我试图实现一个服务,而这个服务的一部分是一个db层.它的设置是这样的,我有一个帮助类,执行get / update方法到数据库和它们之上的层,作为一个看门人.例如：

public class GetStudentDBHelper {
   public List<Student> get(List<Integer> ids) {
      Conn getConnection...
      // run sql query and construct returning Student objects
   }
   public List<Student> get(List<Classroom> byClassroom) {
      // get all students in passed in classrooms
      // run sql query and construct returning Student objects
   }
}

public class StudentJanitor {
   public GetStudentDBHelper getStudentDBHelper;
   public UpdateStudentDBHelper updateStudentDBHelper;
   public UpdateClassroomDBHelper updateClassroomDBHelper;

   public List<Student> getStudents(List<Integer> ids) {
       return getStudentDBHelper.get(ids);
   }

   public void saveStudents(List<Students> students,int classRoomid) {
       Connection conn = Pool.getConnection(); // assume this gives a jdbc
       conn.autocommit(false);

       try {
           try 
           {
              updateStudentDBHelper.saveForClassroom(students,classRoomid,conn);
              updateClassroomDBHelper.markUpdated(classRoomid,conn);
              conn.commit();
           }
           catch
           {
              throw new MyCustomException(ErrorCode.Student);
           }
       }
       catch (sqlException c)
       {
           conn.rollback();
       }
       finally {
           conn.close();
       }
}

public class ClassroomJanitor{
   public void saveClassRoon(List<Classrooms> classrooms) {
       Connection conn = Pool.getConnection()// assume this gives a jdbc
       conn.autocommit(false);

       try {

           try {
              updateClassroomDBHelper.save(classrooms,conn);
              updateStudentDBHelper.save(classrooms.stream().map(Classroom::getStudents).collect(Collections.toList()),conn);
              conn.commit();
           }
           catch {
              throw new MyCustomException(ErrorCode.ClassRoom);
           }
       }
       catch (sqlException c)
       {
           conn.rollback();
       }
       finally {
           conn.close();
       }
}...

public class GetClassroomDBHelper{}...
public class UpdateClassroomDBHelper{}...

更新db类都会组成多个其他更新程序,以防他们需要更新其他表中的值(即保存学生意味着我必须触摸学生所属的课堂表,以更新其上次更新的时间).

我遇到的问题是更新db类,如果我正在触摸多个表,以便拥有交易和回滚功能,我必须从我的Janitor类传递一个连接.看到上面我的意思.有没有更好的方法来做到这一点？这种类型的try,catch,传入conn到db helpers,必须为我的管理器中的任何多事务操作完成.

简而言之,您可以看到代码通常是这样重复的多个方法：

Connection conn = Pool.getConnection()// assume this gives a jdbc
       conn.autocommit(false);

       try {

           try {
              //do some business logic requiring Connection conn
           }
           catch {
              throw new MyCustomException(ErrorCode);
           }
       }
       catch (sqlException c)
       {
           conn.rollback();
       }
       finally {
           conn.close();
       }

解决方法

每当你有一个代码序列是重复的,但它只在一些部分不同,你可以使用一个 template method.

在你的情况下,我将介绍一个TransactionTemplate类,并为不同的部分使用回调接口.例如.

public class TransactionTemplate {

    private DataSource dataSource;

    public TransactionTemplate(DataSource dataSource) {
        this.dataSource = Objects.requireNonNull(dataSource);

    }

    public <T> T execute(TransactionCallback<T> transactionCallback) throws Exception {
        Connection conn = dataSource.getConnection();// assume this gives a jdbc
        try {
            conn.setAutoCommit(false);
            T result = transactionCallback.doInTransaction(conn);
            conn.commit();
            return result;
        } catch (Exception e) {
            conn.rollback();
            throw e;
        } finally {
            conn.close();
        }
    }
}

回调界面看起来像这样

public interface TransactionCallback<T> {
    public T doInTransaction(Connection conn) throws Exception;
}

正如您可以看到TransactionTemplate管理事务,而TransactionCallback实现了在一个事务中必须完成的逻辑.

那么你的客户端代码就会这样

public class StudentJanitor {

    private TransactionTemplate transactionTemplate;

    StudentJanitor(DataSource dataSource) {
        transactionTemplate = new TransactionTemplate(dataSource);
    }

    public void saveStudents(List<Students> students,int classRoomid) {
        SaveStudentsTransaction saveStudentsTransaction = new SaveStudentsTransaction(students,classRoomid);
        transactionTemplate.execute(saveStudentsTransaction);
    }

}

逻辑放在TransactionCallback中

public class SaveStudentsTransaction implements TransactionCallback<Void> {

    public GetStudentDBHelper getStudentDBHelper;
    public UpdateStudentDBHelper updateStudentDBHelper;
    public UpdateClassroomDBHelper updateClassroomDBHelper;

    private List<Students> students;
    private int classRoomid;

    public SaveStudentsTransaction(List<Students> students,int classRoomid) {
        this.students = students;
        this.classRoomid = classRoomid;
    }

    @Override
        public Void doInTransaction(Connection conn) throws Exception {
            try 
            {
               updateStudentDBHelper.saveForClassroom(students,conn);
               updateClassroomDBHelper.markUpdated(classRoomid,conn);
               conn.commit();
            }
            catch
            {
               throw new MyCustomException(ErrorCode.Student);
            }
            return null;
        }

}

java – 数据库设计,不传递jdbc

解决方法

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