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解决冗余代码的三种方法,让你的代码更上一层楼

2023-02-28  51CTO  JAVA旭阳
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前言

冗余代码向来是代码的一种坏味道,也是我们程序员要极力避免的。今天我通过一个示例和大家分享下解决冗余代码的3个手段,看看哪个最好。

问题描述

为了描述这个问题,我将使用 FtpClient 作为示例。要从 ftp 服务器获取一些文件,你需要先建立连接,下一步是登录,然后执行查看ftp文件列表、删除ftp文件,最后注销并断开连接, 代码如下:

public class FtpProvider{

    private final FTPClient ftpClient;

    public FTPFile[] listDirectories(String parentDirectory) {
        try {
            ftpClient.connect("host", 22);
            ftpClient.login("username", "password");
            return ftpClient.listDirectories(parentDirectory);
        } catch (IOException ex) {
            log.error("Something went wrong", ex);
            throw new RuntimeException(ex);
        } finally {
            try {
                ftpClient.logout();
                ftpClient.disconnect();
            } catch (IOException ex) {
                log.error("Something went wrong while finally", ex);
            }
        }
    }

    public boolean deleteFile(String filePath) {
        try {
            ftpClient.connect("host", 22);
            ftpClient.login("username", "password");
            return ftpClient.deleteFile(filePath);
        } catch (IOException ex) {
            log.error("Something went wrong", ex);
            throw new RuntimeException(ex);
        } finally {
           try {
                ftpClient.logout();
                ftpClient.disconnect();
            } catch (IOException ex) {
                log.error("Something went wrong while finally", ex);
            }
        }
    }
}

正如上面代码所示,listDirectories和downloadFtpFile​中都包含了ftp连接、登录以及最后的注销操作,存在大量冗余的代码,那有什么更好的办法清理冗余代码呢?下面推荐3个做法,所有三个提出的解决方案都将实现以下 FtpProvider 接口,我将比较这些实现并选择更好的一个。

public interface FtpProvider {

    FTPFile[] listDirectories(String directory) throws IOException;

    boolean deleteFile(String filePath) throws IOException;
}

1. 使用@Aspect 代理

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface FtpOperation {
}
@Slf4j
@Service
class FtpProviderImpl implements FtpProvider {

    private final FTPClient ftpClient;

    @Override
    public FTPFile[] listDirectories(String directory) throws IOException {
        return ftpClient.listDirectories(directory);
    }

    @Override
    public boolean deleteFile(String filePath) throws IOException {
       return ftpClient.deleteFile(filePath);
    }
}
@Slf4j
@Aspect
@Component
@RequiredArgsConstructor
public class FtpOperationProxy {

    private final FTPClient ftpClient;
    
    @Around("@annotation(daniel.zielinski.redundancy.proxyaop.infrastructure.FtpOperation)")
    public Object handle(ProceedingJoinPoint joinPoint) throws Throwable {
        try {
            ftpClient.connect("host", 22);
            ftpClient.login("username", "password");
            return joinPoint.proceed();
        } catch (IOException ex) {
            log.error("Something went wrong", ex);
            throw new RuntimeException(ex);
        } finally {
            try {
                ftpClient.logout();
                ftpClient.disconnect();
            } catch (IOException ex) {
                log.error("Something went wrong while finally", ex);
            }
        }
    }
}

所有用@FtpOperation​ 注解的方法都会在这个地方执行joinPoint.proceed()。

2. 函数式接口

@FunctionalInterface
interface FtpOperation<T, R> {
      
     R Apply(T t) throws IOException;
}
@RequiredArgsConstructor
@Slf4j
@Service
public class FtpOperationTemplate {

    private final FTPClient ftpClient;

    public <K> K execute(FtpOperation<FTPClient, K> ftpOperation) {
        try {
            ftpClient.connect("host", 22);
            ftpClient.login("username", "password");
            return ftpOperation.apply(ftpClient);
        } catch (IOException ex) {
            log.error("Something went wrong", ex);
            throw new RuntimeException(ex);
        } finally {
            try {
                ftpClient.logout();
                ftpClient.disconnect();
            } catch (IOException ex) {
                log.error("Something went wrong while finally", ex);
            }
        }
    }

}
@RequiredArgsConstructor
@Slf4j
@Service
class FtpProviderFunctionalInterfaceImpl implements FtpProvider {

    private final FtpOperationTemplate ftpOperationTemplate;

    public FTPFile[] listDirectories(String parentDirectory) {
        return ftpOperationTemplate.execute(ftpClient -> ftpClient.listDirectories(parentDirectory));
    }

    public boolean deleteFile(String filePath) {
        return ftpOperationTemplate.execute(ftpClient -> ftpClient.deleteFile(filePath));
    }
}

我们正在 FtpOperationTemplate​ 上执行方法 execute​ 并且我们正在传递 lambda​ 表达式。我们将放入 lambda​ 中的所有逻辑都将代替 ftpOperation.apply(ftpClient) 函数执行。

3. 模板方法

@RequiredArgsConstructor
@Slf4j
@Service
abstract class FtpOperationTemplate<T, K> {

    protected abstract K command(FTPClient ftpClient, T input) throws IOException;

    public K execute(FTPClient ftpClient, T input) {
        try {
            ftpClient.connect("host", 22);
            ftpClient.login("username", "password");
            return command(ftpClient, input);
        } catch (IOException ex) {
            log.error("Something went wrong", ex);
            throw new RuntimeException(ex);
        } finally {
            try {
                ftpClient.logout();
                ftpClient.disconnect();
            } catch (IOException ex) {
                log.error("Something went wrong while finally", ex);
            }
        }
    }

}
@Slf4j
@Service
class FtpOperationListDirectories extends FtpOperationTemplate<String, FTPFile[]> {

    @Override
    protected FTPFile[] command(FTPClient ftpClient, String input) throws IOException {
        return ftpClient.listDirectories(input);
    }
}
 
@Slf4j
@Service
class FtpOperationDeleteFile extends FtpOperationTemplate<String, Boolean> {

    @Override
    protected Boolean command(FTPClient ftpClient, String input) throws IOException {
        return ftpClient.deleteFile(input);
    }
}
 
@RequiredArgsConstructor
@Slf4j
@Service
public class FtpProviderTemplateImpl implements FtpProvider {

    private final FtpOperationTemplate<String, FTPFile[]> ftpOperationListDirectories;
    private final FtpOperationTemplate<String, Boolean> ftpOperationDeleteFile;
    private final FTPClient ftpClient;

    public FTPFile[] listDirectories(String parentDirectory) {
        return ftpOperationListDirectories.execute(ftpClient, parentDirectory);
    }

    public boolean deleteFile(String filePath) {
        return ftpOperationDeleteFile.execute(ftpClient, filePath);
    }
}

我们正在 FtpOperationTemplate​ 上执行方法 execute​ 并在那里传递我们的参数。因此执行方法的逻辑对于 FtpOperationTemplate 的每个实现都是不同的。

总结

我们现在来比较下上面种方式:

向 FtpProvider​ 接口添加一个新方法,需要我们仅在一个地方进行更改。我们可以轻松地将我们的 FtpProvider​ 注入到其他服务中。此解决方案的强项可能是 @FtpOperation​ 注释,它可以在 FtpProvider 上下文实现之外使用,但是将 Ftp 操作的逻辑划分到单独的类中并不是一个好方法。

向接口 FtpProvider​ 添加一个新方法,需要我们仅在一个地方进行更改。我们可以轻松地将我们的 FtpProvider 注入到其他服务中。我们将ftp操作的逻辑封装在一个类中。相对于上面的方式,我们也没有用到AOP的库,所以我个人还是比较推荐的。

向接口 FtpProvider​ 添加一个新方法,需要我们在两个地方进行更改。我们需要添加一个新的类,会导致类爆炸,另外,我们还需要将实现注入到 FtpProvider。

如果是你,你会选择哪种方式呢?还是有更好的方法?

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