用于查找会话引用的给定类的所有实例和子实例的 OQL 查询

发布于 2024-08-30 02:15:22 字数 563 浏览 10 评论 0原文

我正在尝试使用 jhat/OQL 来跟踪 Tomcat 容器中的内存泄漏。我想问的问题是：

“显示可从 javax.servlet.http.HttpSession 访问的 foo.bar.Cacheable 类的所有实例（和子实例）”

我设法来了与以下内容一起，但这不显示 foo.bar.Cacheable 的子类（这很重要，因为这实际上是一个接口）。

select filter(reachables(s), "/foo.bar.Cacheable/(classof(it).name)") from javax.servlet.http.HttpSession s

我尝试了下面概念的各种排列，但不断收到错误（“foo”未定义）。

select filter(reachables(s), classof(it) instanceof foo.bar.Cacheable) from javax.servlet.http.HttpSession s

任何人都可以帮我解决通过 OQL 提出这个问题的错误吗？

原文

I'm trying to use jhat/OQL to trace a memory leak in our Tomcat container. The question I want to ask is:

"Show me all the instances (and sub-instances) of foo.bar.Cacheable class that are reachable from javax.servlet.http.HttpSession"

I managed to come up with the following, but this doesn't show subclasses of foo.bar.Cacheable (which is important since this is infact an interface).

select filter(reachables(s), "/foo.bar.Cacheable/(classof(it).name)") from javax.servlet.http.HttpSession s

I tried various permutations of the concept below, but just keep getting errors ("foo" is not defined).

select filter(reachables(s), classof(it) instanceof foo.bar.Cacheable) from javax.servlet.http.HttpSession s

Can anyone help me out with what I'm doing wrong to pose this question through OQL?

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寄居人 2024-09-06 02:15:22

在基于 jhat 的 OQL 实现（jHat、VisualVM）中，您可以利用这样一个事实：您不仅限于类似 SQL 的语法，而且拥有完整的 javascript 引擎。

下面的代码可以解决这个问题

var containerSuperClass = "javax.servlet.http.HttpSession"
var elementSuperClass = "foo.bar.Cacheable"
// find the container class by name
var alClz = heap.findClass(elementSuperClass)
// retrieve all subclasses
var subClzs = alClz.subclasses()

// filter the list of objects reachables from instances of the container super class
// and all its subclasses so it contains only objects of classes from subClzs
map(heap.objects(containerSuperClass), 'filter(reachables(it), "it != null && contains(subClzs, containsClause(it))")')

// we need to externalize the contains clause because of clash in naming the closure parameter 'it'
function containsClause(rcbl) {
    return function(it) {
        if (rcbl == null || it == null) return false;
        return it.name.equals(classof(rcbl).name)
    }
}

In jhat based OQL implementations (jHat, VisualVM) you can exploit the fact that you are not limited to the SQL like syntax but you have a complete javascript engine at your hands.

The following piece of code would do the trick

var containerSuperClass = "javax.servlet.http.HttpSession"
var elementSuperClass = "foo.bar.Cacheable"
// find the container class by name
var alClz = heap.findClass(elementSuperClass)
// retrieve all subclasses
var subClzs = alClz.subclasses()

// filter the list of objects reachables from instances of the container super class
// and all its subclasses so it contains only objects of classes from subClzs
map(heap.objects(containerSuperClass), 'filter(reachables(it), "it != null && contains(subClzs, containsClause(it))")')

// we need to externalize the contains clause because of clash in naming the closure parameter 'it'
function containsClause(rcbl) {
    return function(it) {
        if (rcbl == null || it == null) return false;
        return it.name.equals(classof(rcbl).name)
    }
}

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