确保弹簧组件是无状态的 [英] Make sure spring component is stateless

问题描述

当开发人员向Spring组件引入可变性时，我们遇到了多线程问题。这样的事情：

We faced a multi-threading problem when a developer introduced mutability to a Spring Component. Something like this:

@Component //singleton
public class MyComponent {
...
private String intermediateResults;
public String businessMethod() {
 ... fills in intermediateResults;
}

public String thisGetterShouldNotBeHere() {
    return intermediateResults;
 }
}

导致多线程的错误 - 字段intermediateResults有从不同的线程访问过。

which led to bug with multithreading - the field intermediateResults has been accessed from different threads.

是否有办法防止向Spring Singleton添加状态，例如通过某种静态分析仪？
SonarQube插件？ Eclipse插件？
感谢您的建议。

Is there are a way to prevent adding state to a Spring Singleton e.g. by some kind of static analyzer? SonarQube plugins? Eclipse plugins? Thanks for suggestions.

推荐答案

Google的 MutabilityDetector 似乎能够完全满足您的需求：

Google's MutabilityDetector seems able to do exactly what you need:

Mutability Detector旨在分析Java类并报告给定类的实例是否是不可变的。它可以使用：

Mutability Detector is designed to analyse Java classes and report on whether instances of a given class are immutable. It can be used:

• 在单元测试中，使用断言如assertImmutable（MyClass.class）。你的班级实际上是不可变的吗？你刚刚做出改变后怎么办？


• 作为一个FindBugs插件。你用@Immutable注释的那些类实际上是吗？
  在运行时。您的API是否需要被赋予不可变对象？
  从命令行。你想在整个代码库中快速运行Mutability Detector吗？

我会建议你添加一个明确的合同，声明该类应该是不可变的，可以通过 javadoc 或通过 @Immutable 类注释本身，允许（明智的）开发人员维护类的必需品。 （如果Google的检测器未能检测到特定类型的不变性，例如：字符串，日期真的不可变吗？）

I would anyway advise to add a clear contract stating that the class is supposed to be immutable either via javadoc or via @Immutable annotation on the class itself, to allow (sensible) developers to maintain the class requisites. (In case Google's detector fails to detect specific types of immutability eg: Are String, Date really immutable?)

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