首页 \ 问答 \ 我的ThreadLocal包含并始终返回null(My ThreadLocal contains and returns null always)

我的ThreadLocal包含并始终返回null(My ThreadLocal contains and returns null always)

 我想知道当我将threadlocal.set（）设置为32个元素的集合时，它是如何存储数据的。 ThreadLocal.get（）始终返回null; 对应的FutureTask对象有一个结果属性= NullPointerException。 知道为什么ThreadLocal无法存储集合项吗？  
public class MyCallable<T> implements Callable<Collection<T>> {

    public MyCallable( Collection<T> items ){
        tLocal = new ThreadLocal<Collection<T>>();
        tLocal.set( items );                    //SETS NULL ALTHOUGH the PARAMETER CONTAINS 32 ITEMS
    }

    @Override
    @SuppressWarnings("unchecked")
    public Collection<T> call() throws Exception {
        synchronized( lock ){
            ArrayList<T> _items = new ArrayList<T>();
            ArrayList<T> _e = ( ArrayList<T> ) tLocal.get();   //RETURNS NULL
            for( T item : _e ){
                _items = getPValue( item ));
            }
            return _items ;
        }
    }

    private ThreadLocal<Collection<T>> tLocal;

    private final Object lock = new Object();
}
 
 用法片段：  
List<Future<Collection<T>>> futures = new ArrayList<Future<Collection<T>>>();
ExecutorService pool = Executors.newFixedThreadPool( 8 );

        for( int x = 0; x < numBatches; ++x ){
            List<T> items = retrieveNext32Items( x );
            futures.add( pool.submit( new MyCallable<T>( items ));
        }

        pool.shutdown();

        for( Future<Collection<T>> future : futures ) {
            _items.addAll( future.get() );                  //future.outcome = NullPointerException 
        }

        return _items
}

I am wondering how the threadlocal.set() has no data stored when I set it to a collection of 32 elements. ThreadLocal.get() returns null always; and the correspoding FutureTask object has an outcome property = NullPointerException. Any idea why ThreadLocal is unable to store collection items? 
public class MyCallable<T> implements Callable<Collection<T>> {

    public MyCallable( Collection<T> items ){
        tLocal = new ThreadLocal<Collection<T>>();
        tLocal.set( items );                    //SETS NULL ALTHOUGH the PARAMETER CONTAINS 32 ITEMS
    }

    @Override
    @SuppressWarnings("unchecked")
    public Collection<T> call() throws Exception {
        synchronized( lock ){
            ArrayList<T> _items = new ArrayList<T>();
            ArrayList<T> _e = ( ArrayList<T> ) tLocal.get();   //RETURNS NULL
            for( T item : _e ){
                _items = getPValue( item ));
            }
            return _items ;
        }
    }

    private ThreadLocal<Collection<T>> tLocal;

    private final Object lock = new Object();
}
 
usage snippet: 
List<Future<Collection<T>>> futures = new ArrayList<Future<Collection<T>>>();
ExecutorService pool = Executors.newFixedThreadPool( 8 );

        for( int x = 0; x < numBatches; ++x ){
            List<T> items = retrieveNext32Items( x );
            futures.add( pool.submit( new MyCallable<T>( items ));
        }

        pool.shutdown();

        for( Future<Collection<T>> future : futures ) {
            _items.addAll( future.get() );                  //future.outcome = NullPointerException 
        }

        return _items
}

原文：https://stackoverflow.com/questions/31958871

更新时间：2023-05-18 06:05

最满意答案

 您最好的选择是使用量角器的内置命令行选项来传递浏览器或在任何此类功能之间切换。  
Usage: protractor [configFile] [options]
configFile defaults to protractor.conf.js
The [options] object will override values from the config file.
See the reference config for a full list of options.

Options:
--help                                 Print Protractor help menu
--version                              Print Protractor version
--browser, --capabilities.browserName  Browsername, e.g. chrome or firefox
 
 如果您查看量角器的cli选项 ，如果您在multicapabilties选项中设置了多个浏览器，则可以传递这样的浏览器名称 -  
protractor config.js --capabilities.browserName='chrome'
protractor config.js --capabilities.browserName='firefox'
 
 您可以将其设置为package.json中的单个脚本，以在各种浏览器中运行测试 -  
"scripts": {
"tsc": "tsc",
"test": "protractor ./config.js",
"chrome-tests": "protractor ./config.js --capabilities.browserName='chrome'",
"firefox-tests": "protractor ./config.js --capabilities.browserName='firefox'"
}
 
 现在你可以使用npm来调用它 -  
npm run chrome-tests // it would run your tests in chrome browser
npm run firefox-tests // it would run your tests in firefox browser
 
 您还可以在conf文件中使用params对象传递参数，并在测试或命令行中的任何位置访问它们。  
params: {
     primaryBrowser: 'chrome'  // I am biased towards chrome :)
     secondaryBrowser: 'firefox'
 },
 
 您可以通过起诉浏览器的全局对象在测试中访问它们 -  
console.log(browser.params.primaryBrowser);
console.log(browser.params.secondaryBrowser);
 
 同样，您可以在命令行中更改它们 -  
protractor config.js --params.primaryBrowser='firefox'
 
 通过getMultiCapabilities有一种更优雅的方式来做这些事情 -  
 您甚至可以通过访问上述函数对象来传递多个浏览器，请参阅此链接以获取更多详细信息。  
 有没有办法通过量角器cli传递多个浏览器 

Your best bet would be to use protractor's in-built command line options for passing browsers or toggling between any such capabilities. 
Usage: protractor [configFile] [options]
configFile defaults to protractor.conf.js
The [options] object will override values from the config file.
See the reference config for a full list of options.

Options:
--help                                 Print Protractor help menu
--version                              Print Protractor version
--browser, --capabilities.browserName  Browsername, e.g. chrome or firefox
 
If you look at the protractor's cli options and if you have more than one browsers setup in your multicapabilties option, you can pass browser names like this - 
protractor config.js --capabilities.browserName='chrome'
protractor config.js --capabilities.browserName='firefox'
 
You can set this as individual scripts in your package.json to run tests in various browsers-  
"scripts": {
"tsc": "tsc",
"test": "protractor ./config.js",
"chrome-tests": "protractor ./config.js --capabilities.browserName='chrome'",
"firefox-tests": "protractor ./config.js --capabilities.browserName='firefox'"
}
 
Now you can invoke this by using npm - 
npm run chrome-tests // it would run your tests in chrome browser
npm run firefox-tests // it would run your tests in firefox browser
 
You can also make use params object in your conf file pass paramaters and access them anywhere in your tests or command line. 
params: {
     primaryBrowser: 'chrome'  // I am biased towards chrome :)
     secondaryBrowser: 'firefox'
 },
 
You can access them in your tests by suing browser's global object - 
console.log(browser.params.primaryBrowser);
console.log(browser.params.secondaryBrowser);
 
Similarly you can change them in your command line- 
protractor config.js --params.primaryBrowser='firefox'
 
There is one more elegant way of doing such things through getMultiCapabilities-  
You can even pass multiple browsers by accessing the above functions object, please refer this link for more details. 
Is there any way to pass multiple browser via protractor cli

我的ThreadLocal包含并始终返回null(My ThreadLocal contains and returns null always)

最满意答案

相关问答

通过标签使用黄瓜VCR(Using VCR with Cucumber via tags)[2021-08-20]

在运行rspec时，无法加载这样的文件 - cucumber-rails(getting cannot load such file — cucumber-rails when running rspec)[2023-07-13]

是否有可能根据所使用的标签（或不是）在黄瓜步骤中执行不同的操作？(Is it possible to perform different actions in a Cucumber step based on the tag used (or not)?)[2023-09-11]

匹配输入标签与Cucumber / Webrat(Matching input tag with Cucumber/Webrat)[2023-04-28]

从IntelliJ（OSX）启动Ruby-Cucumber(Launching Ruby-Cucumber from IntelliJ (OSX))[2023-09-21]

Rails：让Settingslogic在Cucumber上工作(Rails: Making Settingslogic work with Cucumber)[2022-01-01]

量角器配置文件使用茉莉和黄瓜规格(Protractor config file to use both jasmine and cucumber specs)[2022-09-09]

Webdriverio（WDIO）和基于Tag的Cucumber浏览器(Webdriverio (WDIO) and Cucumber Browser based on Tag)[2023-05-18]

基于黄瓜标签切换multiCapabilites配置(Toggling multiCapabilites config based on cucumber tag)[2023-02-02]

我们是否可以列出属于Cucumber标签的所有场景(Can we list all the scenarios which fall under a Cucumber tag)[2023-04-07]

相关文章

最新问答