Java 从 DAO 中删除重复的 try、catch、finally 样板文件

Question

我有一个包含许多方法的 DAO 类，这些方法有很多重复的代码:-

public void method1(...) {
  Connection conn = null;
  try {
      //custom code here
  } catch (SQLException e) {
     LOG.error("Error accessing the database.", e);
     throw new DatabaseException();
  } catch (QueryNotFoundException e) {
     LOG.error("Error accessing the database.", e);
     throw new DatabaseException();
  } finally {
     if (conn != null)
        connectionPool.returnConnection(conn);
  } 

public void method2(...) {
  Connection conn = null;
  try {
      //different custom code here
  } catch (SQLException e) {
     LOG.error("Error accessing the database.", e);
     throw new DatabaseException();
  } catch (QueryNotFoundException e) {
     LOG.error("Error accessing the database.", e);
     throw new DatabaseException();
  } finally {
     if (conn != null)
        connectionPool.returnConnection(conn);
  } 

我想重组这个类，将 try、catch、finally 放在一个地方以避免重复。我将如何做到这一点？

Answer 1

为ex创建一个接口(interface)。可执行文件:

 public interface Executable() {

   void exec() throws SqlException();

 }

将您的每个 dao 方法重构为:

public void method1() {
   execute(new Executable() {

     @Override
     public void exec() throws SqlException() {
          // your code here
     }
  });
  } 

在您的 DAO 中创建以下方法执行:

private void execute(Executor ex) {
    try {
      ex.exec();
    } catch(...) {
      ...
    } finally {
       ...
    }
}