如何编写注释/方面以不输入方法但如果给定条件为假则返回null？ [英] How to write an annotation/aspect to not enter a method but return null if a given condition is false?

问题描述

我目前有一个要求，如果给定条件为false，我需要从100个方法返回null。我正在考虑使用Java Annotations或Spring Aspects，这样我就不必在任何地方编写if-else代码块。有关如何使用Java Annotations或Spring Aspects执行此操作的任何想法？

I currently have a requirement where I need to return null from 100s of methods if a given condition is false. I was thinking of using Java Annotations or Spring Aspects for this so that I don't have to write that if-else block of code everywhere. Any idea as to how we can do this using Java Annotations or Spring Aspects?

任何指针都可能有所帮助。

Any pointers might be helpful.

推荐答案

没有春天，你可以使用纯AspectJ：

Without spring you could use pure AspectJ:

Demo.java：我们想要修改的方法示例

Demo.java : example of the method we want to modify

public class Demo {
    public String boom(String base) {
        return base;
    }
}

DemoAspect.aj：配置文件。 使用入门。在AspectJ中，切入点选择某些加入程序流程中的要点。为了实际实现横切行为，我们使用建议。 建议汇集切入点（选择） out join points）和一组代码（在每个连接点上运行）：before，around，after ...

DemoAspect.aj : configuration file. Getting started. In AspectJ, pointcuts pick out certain join points in the program flow. To actually implement crosscutting behavior, we use advice. Advice brings together a pointcut (to pick out join points) and a body of code (to run at each of those join points): before, around, after...

public aspect DemoAspect {
    pointcut callBoom(String base, Demo demo) : 
            call(String Demo.boom(String)) && args(base) && target(demo);

    String around(String base, Demo demo) : callBoom(base, demo){
        if ("detonate".equals(base)) {
            return "boom!";
        } else {
            return proceed(base, demo);
        }
    }
}

DemoTest.java

DemoTest.java

public class DemoTest {
    @Test
    void name() {
        Demo demo = new Demo();
        assertEquals("boom!", demo.boom("detonate"));
        assertEquals("fake", demo.boom("fake"));
    }
}

将依赖项添加到 pom。 xml

    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjrt</artifactId>
        <version>1.8.13</version>
    </dependency>
    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjweaver</artifactId>
        <version>1.8.13</version>
    </dependency>

和插件一样，注意版本。例如1.11插件需要1.8.13库。

And plugin, pay attention to the versions. For example 1.11 plugin expects 1.8.13 libraries.

<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>aspectj-maven-plugin</artifactId>
    <version>1.11</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>
                <!-- use this goal to weave all your main classes -->
                <goal>compile</goal>
                <!-- use this goal to weave all your test classes -->
                <goal>test-compile</goal>
            </goals>
        </execution>
    </executions>
</plugin>

有更多细节的好例子， Baeldung 。 官方文档。

Good example with more details, Baeldung. Official documentation.

这篇关于如何编写注释/方面以不输入方法但如果给定条件为假则返回null？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！