java - Spring /SPeL : condition specific Cache control from one class to another

Question

tl;博士;

我正在寻找一种方法来在另一个类的 Spring Cacheable 注释上设置“条件”属性。有这样的办法吗？

使用 Spring Cache，它应该仅在调用某个方法时进行缓存。这个方法在ClassA中，要缓存的方法(数据)在ClassB中。我想做的是这样的:

public ClassA implements myInterface {
...  
    private Boolean inProcess = false;

    public void cacheWhenThisMethodCalled() {
        try {
            inProcess = true;
            // do work here, somewhere along the line
            // the method in ClassB gets called
        } finally {
            inProcess = false;
        }
 }

B类:

public ClassB {
...
    @Cacheable(cacheNames={"aCache"}, condition="#classA.inProcess")
    public ValueClass findValueClass(UUID id)

但是，我找不到 SPeL 工作的合适条件。我尝试了很多组合，但没有成功。 ClassA 是一个 SpringBean，但是 @Bean 注解返回的是 Interface，而不是类。这可以发挥作用吗？或者有更好的办法吗？

Answer 1

使用ThreadLocal - 为了线程安全，无论如何你都需要这样做 - 否则不同的线程可以更改该字段。

这很好用...

@SpringBootApplication
@EnableCaching
public class So47580936Application {

    public static void main(String[] args) {
        SpringApplication.run(So47580936Application.class, args);
    }

    @Bean
    public ApplicationRunner runner(Bar bar) {
        return args -> {
            bar.cacheFromHere();
            bar.dontCacheFromHere();
        };
    }

    @Component
    public static class Foo {

        @Cacheable(cacheNames = "foos", condition = "T(com.example.So47580936Application$Bar).cacheit()")
        public String foo() {
            System.out.println("here");
            return "foo";
        }

    }

    @Component
    public static class Bar {

        private static final ThreadLocal<Boolean> cacheit = new ThreadLocal<>();

        @Autowired
        private Foo foo;

        public static boolean cacheit() {
            return cacheit.get() == null ? false : cacheit.get();
        }

        public void cacheFromHere() {
            try {
                this.cacheit.set(true);
                System.out.println("Cache:" + this.foo.foo());
                System.out.println("Cache:" + this.foo.foo());
            }
            finally {
                this.cacheit.remove();
            }
        }

        public void dontCacheFromHere() {
            System.out.println("Don't:" + this.foo.foo());
            System.out.println("Don't:" + this.foo.foo());
        }

    }

}

结果:

here
Cache:foo
Cache:foo
here
Don't:foo
here
Don't:foo

编辑

或者，您可以将 ThreadLocal 设为 @Bean ...

@SpringBootApplication
@EnableCaching
public class So47580936Application {

    public static void main(String[] args) {
        SpringApplication.run(So47580936Application.class, args);
    }

    @Bean
    public ApplicationRunner runner(Bar bar) {
        return args -> {
            bar.cacheFromHere();
            bar.dontCacheFromHere();
        };
    }

    @Bean
    public ThreadLocal<Boolean> cacheit() {
        return new ThreadLocal<>();
    }

    @Component
    public static class Foo {

        @Cacheable(cacheNames = "foos", condition = "@cacheit.get() ?: false")
        public String foo() {
            System.out.println("here");
            return "foo";
        }

    }

    @Component
    public static class Bar {

        @Autowired
        private ThreadLocal<Boolean> cacheit;

        @Autowired
        private Foo foo;

        public void cacheFromHere() {
            try {
                this.cacheit.set(true);
                System.out.println("Cache:" + this.foo.foo());
                System.out.println("Cache:" + this.foo.foo());
            }
            finally {
                this.cacheit.remove();
            }
        }

        public void dontCacheFromHere() {
            System.out.println("Don't:" + this.foo.foo());
            System.out.println("Don't:" + this.foo.foo());
        }

    }

}