Java通過Lambda表達(dá)式實現(xiàn)簡化代碼

更新時間：2023年05月22日 15:21:26 作者：BillySir

我們在編寫代碼時，常常會遇到代碼又長又重復(fù)的情況，就像調(diào)用第3方服務(wù)時，每個方法都差不多,?寫起來啰嗦,?改起來麻煩,?還容易改漏，所以本文就來用Lambda表達(dá)式簡化一下代碼，希望對大家有所幫助

之前，調(diào)用第3方服務(wù)，每個方法都差不多“長”這樣, 寫起來啰嗦, 改起來麻煩, 還容易改漏。

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;
    }
}

我經(jīng)過學(xué)習(xí)和提取封裝, 將try ... catch ... catch .. 提取為公用, 得到這2個方法:

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);
}

現(xiàn)在用起來是如此簡潔。像這種無返回值的:

public void authorizeRoleToUser(Long userId, List<Long> roleIds) {
    tryCatch(() -> { power.authorizeRoleToUser(userId, roleIds); }, "Power", "authorizeRoleToUser");
}

還有這種有返回值的:

public List<RoleDTO> listRoleByUser(Long userId) {
    return tryCatch(() -> power.listRoleByUser(userId), "Power", "listRoleByUser");
}

后來發(fā)現(xiàn)以上2個方法還不夠用, 原因是有一些方法會拋出 checked 異常, 于是又再添加了一個能處理異常的, 這次意外發(fā)現(xiàn)Java的throws也支持泛型, 贊一個:

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;
}

為了不至于維護(hù)兩份catch集, 將原來的帶返回值的tryCatch改為調(diào)用tryCatchException:

public static <T> T tryCatch(Supplier<T> supplier, String serviceName, String methodName) {
    return tryCatchException(() -> supplier.get(), serviceName, methodName);
}

這個世界又完善了一步。

前面制作了3種情況:

1.無返回值,無 throws

2.有返回值,無 throws

3.有返回值,有 throws

不確定會不會出現(xiàn)“無返回值，有throws“的情況。后來真的出現(xiàn)了！依樣畫葫蘆，弄出了這個：

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;
}

完整代碼

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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