Java通过Lambda表达式实现简化代码
作者:BillySir
我们在编写代码时,常常会遇到代码又长又重复的情况,就像调用第3方服务时,每个方法都差不多, 写起来啰嗦, 改起来麻烦, 还容易改漏,所以本文就来用Lambda表达式简化一下代码,希望对大家有所帮助
之前,调用第3方服务,每个方法都差不多“长”这样, 写起来啰嗦, 改起来麻烦, 还容易改漏。
public void authorizeRoleToUser(Long userId, List<Long> roleIds) { try { power.authorizeRoleToUser(userId, roleIds); } catch (MotanCustomException ex) { if (ex.getCode().equals(MSUserException.notLogin().getCode())) throw UserException.notLogin(); if (ex.getCode().equals(MSPowerException.haveNoPower().getCode())) throw PowerException.haveNoPower(); throw ex; } catch (MotanServiceException ex) { CatHelper.logEventService("Power-authorizeRoleToUser", "authorizeRoleToUser", ex.getStatus(), ex.getErrorCode(), ex.getMessage()); throw ex; } catch (MotanAbstractException ex) { CatHelper.logEventService("Power-authorizeRoleToUser", "authorizeRoleToUser", ex.getStatus(), ex.getErrorCode(), ex.getMessage()); throw ex; } catch (Exception ex) { CatHelper.logError(ex); throw ex; } }
我经过学习和提取封装, 将try ... catch ... catch .. 提取为公用, 得到这2个方法:
import java.util.function.Supplier; public static <T> T tryCatch(Supplier<T> supplier, String serviceName, String methodName) { try { return supplier.get(); } catch (MotanCustomException ex) { if (ex.getCode().equals(MSUserException.notLogin().getCode())) throw UserException.notLogin(); if (ex.getCode().equals(MSPowerException.haveNoPower().getCode())) throw PowerException.haveNoPower(); throw ex; } catch (MotanServiceException ex) { CatHelper.logEventService(serviceName + "-" + methodName, methodName, ex.getStatus(), ex.getErrorCode(), ex.getMessage()); throw ex; } catch (MotanAbstractException ex) { CatHelper.logEventService(serviceName + "-" + methodName, methodName, ex.getStatus(), ex.getErrorCode(), ex.getMessage()); throw ex; } catch (Exception ex) { CatHelper.logError(ex); throw ex; } } public static void tryCatch(Runnable runnable, String serviceName, String methodName) { tryCatch(() -> { runnable.run(); return null; }, serviceName, methodName); }
现在用起来是如此简洁。像这种无返回值的:
public void authorizeRoleToUser(Long userId, List<Long> roleIds) { tryCatch(() -> { power.authorizeRoleToUser(userId, roleIds); }, "Power", "authorizeRoleToUser"); }
还有这种有返回值的:
public List<RoleDTO> listRoleByUser(Long userId) { return tryCatch(() -> power.listRoleByUser(userId), "Power", "listRoleByUser"); }
后来发现以上2个方法还不够用, 原因是有一些方法会抛出 checked 异常, 于是又再添加了一个能处理异常的, 这次意外发现Java的throws也支持泛型, 赞一个:
public static <T, E extends Throwable> T tryCatchException(SupplierException<T, E> supplier, String serviceName, String methodName) throws E { try { return supplier.get(); } catch (MotanCustomException ex) { if (ex.getCode().equals(MSUserException.notLogin().getCode())) throw UserException.notLogin(); if (ex.getCode().equals(MSPowerException.haveNoPower().getCode())) throw PowerException.haveNoPower(); throw ex; } catch (MotanServiceException ex) { CatHelper.logEventService(serviceName + "-" + methodName, methodName, ex.getStatus(), ex.getErrorCode(), ex.getMessage()); throw ex; } catch (MotanAbstractException ex) { CatHelper.logEventService(serviceName + "-" + methodName, methodName, ex.getStatus(), ex.getErrorCode(), ex.getMessage()); throw ex; } catch (Exception ex) { CatHelper.logError(ex); throw ex; } } @FunctionalInterface public interface SupplierException<T, E extends Throwable> { /** * Gets a result. * * @return a result */ T get() throws E; }
为了不至于维护两份catch集, 将原来的带返回值的tryCatch改为调用tryCatchException:
public static <T> T tryCatch(Supplier<T> supplier, String serviceName, String methodName) { return tryCatchException(() -> supplier.get(), serviceName, methodName); }
这个世界又完善了一步。
前面制作了3种情况:
1.无返回值,无 throws
2.有返回值,无 throws
3.有返回值,有 throws
不确定会不会出现“无返回值,有throws“的情况。后来真的出现了!依样画葫芦,弄出了这个:
public static <E extends Throwable> void tryCatchException(RunnableException<E> runnable, String serviceName, String methodName) throws E { tryCatchException(() -> { runnable.run(); return null; }, serviceName, methodName); } @FunctionalInterface public interface RunnableException<E extends Throwable> { void run() throws E; }
完整代码
package com.company.system.util; import java.util.function.Supplier; import org.springframework.beans.factory.BeanCreationException; import com.company.cat.monitor.CatHelper; import com.company.system.customException.PowerException; import com.company.system.customException.ServiceException; import com.company.system.customException.UserException; import com.company.hyhis.ms.user.custom.exception.MSPowerException; import com.company.hyhis.ms.user.custom.exception.MSUserException; import com.company.hyhis.ms.user.custom.exception.MotanCustomException; import com.weibo.api.motan.exception.MotanAbstractException; import com.weibo.api.motan.exception.MotanServiceException; public class ThirdParty { public static void tryCatch(Runnable runnable, String serviceName, String methodName) { tryCatch(() -> { runnable.run(); return null; }, serviceName, methodName); } public static <T> T tryCatch(Supplier<T> supplier, String serviceName, String methodName) { return tryCatchException(() -> supplier.get(), serviceName, methodName); } public static <E extends Throwable> void tryCatchException(RunnableException<E> runnable, String serviceName, String methodName) throws E { tryCatchException(() -> { runnable.run(); return null; }, serviceName, methodName); } public static <T, E extends Throwable> T tryCatchException(SupplierException<T, E> supplier, String serviceName, String methodName) throws E { try { return supplier.get(); } catch (MotanCustomException ex) { if (ex.getCode().equals(MSUserException.notLogin().getCode())) throw UserException.notLogin(); if (ex.getCode().equals(MSPowerException.haveNoPower().getCode())) throw PowerException.haveNoPower(); throw ex; } catch (MotanServiceException ex) { CatHelper.logEventService(serviceName + "-" + methodName, methodName, ex.getStatus(), ex.getErrorCode(), ex.getMessage()); throw ex; } catch (MotanAbstractException ex) { CatHelper.logEventService(serviceName + "-" + methodName, methodName, ex.getStatus(), ex.getErrorCode(), ex.getMessage()); throw ex; } catch (Exception ex) { CatHelper.logError(ex); throw ex; } } @FunctionalInterface public interface RunnableException<E extends Throwable> { void run() throws E; } @FunctionalInterface public interface SupplierException<T, E extends Throwable> { T get() throws E; } }
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