如何创建自定义注解拆分请求参数并收集返回结果？

Question

我有一个方法 params 是一个大于 50000 个项目的列表； 受限于业务逻辑，列表必须小于30000，这样我才有办法在逻辑之前把这个数组拆分成二维数组

public static final <T> Collection<List<T>> partitionBasedOnSize(List<T> inputList, int size) {
        AtomicInteger counter = new AtomicInteger(0);
        return inputList.stream().collect(Collectors.groupingBy(s -> counter.getAndIncrement() / size)).values();
}

这是我目前的解决方案：

public List<Account> getChildrenList(List<Long> ids) {
        List<Account> childrenList = new ArrayList<>();
        Collection<List<Long>> childrenId2dList = PartitionArray.partitionBasedOnSize(childrenIdsList, 30000);
        for (List<Long> list : childrenId2dList) {
            //this is my business logic: start
            childrenList.addAll(accountRepository.getAccounts(list));
            //this is my business logic: end
        }
        return childrenAccountsList;
}

我想在方法之上创建一个注释而不是许多重复的代码（每次都检查和尽管...）

对不起，我的英语不好，我画了一个图表： 方法调用>尽管数组>业务逻辑>收集所有结果>返回

Answer 1

在我看来，在这种情况下使用注释有点过度设计（您必须编写注释处理器）。您可以轻松地使用 泛型 和 lambdas 和/或 方法引用 来实现您的目标。例如：

以这种方式更新PartitionArray：

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.Function;
import java.util.stream.Collectors;

public class PartitionArray {

    private static <T> Collection<List<T>> partitionBasedOnSize(List<T> inputList, int partitionSize) {
        Collection<List<T>> collection = new ArrayList<>();
        int remainingSize = inputList.size();
        int index = 0;
        while (remainingSize > partitionSize) {
            collection.add(inputList.subList(index, index + partitionSize));
            remainingSize -= partitionSize;
            index += partitionSize;
        }
        collection.add(inputList.subList(index, index + remainingSize));
        return collection;
    }

    public static <D, T> List<D> partitionAndDoBusinessFunction(List<T> ids, Function<List<T>, List<D>> businessFunction, int partitionSize) {
        List<D> dataList = new ArrayList<>();
        Collection<List<T>> idListCollection = partitionBasedOnSize(ids, partitionSize);
        for (List<T> idList : idListCollection) {
            dataList.addAll(businessFunction.apply(idList));
        }
        return dataList;
    }
}

然后只需从您的AccountService 使用它（使用方法参考）：

import java.util.List;

public class AccountService {

    private AccountRepository accountRepository;

    public List<Account> getAccounts(List<Long> ids) {
        return PartitionArray.partitionAndDoBusinessFunction(ids, accountRepository::getAccounts, 30000);
    }
}

或者使用 lambda：

import java.util.List;

public class AccountService {

    private AccountRepository accountRepository;

    public List<Account> getAccounts(List<Long> ids) {
        return PartitionArray.partitionAndDoBusinessFunction(ids, idList -> {
            List<Account> accounts = accountRepository.getAccounts(idList);
            // do more business on accounts
            return accounts;
        }, 30000);
    }
}

Answer 2

这是一个使用注释的解决方案，使用AspectJ：

首先，定义所需的注解：

package partition;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface Partitioned {

    /**
     * The size of the partition, for instance 30000
     */
    int size();
}

因此您的服务将如下所示：

package partition;

import java.util.List;

public class AccountService {

    private AccountRepository accountRepository;

    public AccountService(AccountRepository accountRepository) {
        this.accountRepository = accountRepository;
    }

    @Partitioned(size = 30000)
    public List<Account> getAccounts(List<Long> ids) {
        return accountRepository.getAccounts(ids);
    }
}

到目前为止，这很容易。然后是注释的处理，AspectJ 进入游戏。定义一个链接到注释的aspect：

package partition;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

@Aspect
public class PartitionedAspect {

    @Pointcut("@annotation(partitioned)")
    public void callAt(Partitioned partitioned) {
    }

    @Around("callAt(partitioned)")
    public <T, D> Object around(ProceedingJoinPoint pjp, Partitioned partitioned) throws Throwable {
        List<T> inputIds = (List) pjp.getArgs()[0];
        if (inputIds.size() > partitioned.size()) {
            List<D> dataList = new ArrayList<>();
            Collection<List<T>> partitionedIds = PartitionArray.partitionBasedOnSize(inputIds, partitioned.size());
            for (List<T> idList : partitionedIds) {
                List<D> data = (List) pjp.proceed(new Object[]{idList});
                dataList.addAll(data);
            }
            return dataList;
        }
        return pjp.proceed();
    }
}

当然，您必须导入 AspectJ，并且还必须在编译时执行一些额外的工作。假设您使用的是 maven，请将这些行添加到您的 pom.xml（插件和依赖项）：

<build>
    <plugins>
        ...
        <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>aspectj-maven-plugin</artifactId>
            <version>1.7</version>
            <configuration>
                <complianceLevel>1.8</complianceLevel>
                <source>1.8</source>
                <target>1.8</target>
                <showWeaveInfo>true</showWeaveInfo>
                <verbose>true</verbose>
                <Xlint>ignore</Xlint>
                <encoding>UTF-8</encoding>
            </configuration>
            <executions>
                <execution>
                    <goals>
                        <goal>compile</goal>
                        <goal>test-compile</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

<dependencies>
    ...
    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjrt</artifactId>
        <version>${aspectj.version}</version>
    </dependency>
    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjweaver</artifactId>
        <version>${aspectj.version}</version>
    </dependency>
...
</dependencies>