Java 无法捕获IOException

一个IOException被抛出，由于某种原因，它不可能被捕获。看看下面的代码。堆栈跟踪表示在调用“apply”-方法时引发IOException。但是，catch子句不会捕获该异常。当我尝试捕获IOException时，Eclipse抱怨说：“IOException的捕获块不可访问。此异常从不从try语句体抛出”

为什么会这样

代码：

这是stacktrace：

java.io.IOException: Unable to download JavaScript from 'somesite' (status 404).
at com.gargoylesoftware.htmlunit.html.HtmlPage.loadJavaScriptFromUrl(HtmlPage.java:1023)
at com.gargoylesoftware.htmlunit.html.HtmlPage.loadExternalJavaScriptFile(HtmlPage.java:967)
at com.gargoylesoftware.htmlunit.html.HtmlScript.executeScriptIfNeeded(HtmlScript.java:353)
at com.gargoylesoftware.htmlunit.html.HtmlScript$1.execute(HtmlScript.java:225)
at com.gargoylesoftware.htmlunit.html.HtmlScript.onAllChildrenAddedToPage(HtmlScript.java:235)
at com.gargoylesoftware.htmlunit.html.HTMLParser$HtmlUnitDOMBuilder.endElement(HTMLParser.java:718)
at org.apache.xerces.parsers.AbstractSAXParser.endElement(Unknown Source)
at com.gargoylesoftware.htmlunit.html.HTMLParser$HtmlUnitDOMBuilder.endElement(HTMLParser.java:676)
at org.cyberneko.html.HTMLTagBalancer.callEndElement(HTMLTagBalancer.java:1136)
at org.cyberneko.html.HTMLTagBalancer.endElement(HTMLTagBalancer.java:1038)
at org.cyberneko.html.filters.DefaultFilter.endElement(DefaultFilter.java:206)
at org.cyberneko.html.filters.NamespaceBinder.endElement(NamespaceBinder.java:329)
at org.cyberneko.html.HTMLScanner$ContentScanner.scanEndElement(HTMLScanner.java:2999)
at org.cyberneko.html.HTMLScanner$ContentScanner.scan(HTMLScanner.java:1991)
at org.cyberneko.html.HTMLScanner.scanDocument(HTMLScanner.java:895)
at org.cyberneko.html.HTMLConfiguration.parse(HTMLConfiguration.java:499)
at org.cyberneko.html.HTMLConfiguration.parse(HTMLConfiguration.java:452)
at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
at com.gargoylesoftware.htmlunit.html.HTMLParser$HtmlUnitDOMBuilder.parse(HTMLParser.java:896)
at com.gargoylesoftware.htmlunit.html.HTMLParser.parse(HTMLParser.java:350)
at com.gargoylesoftware.htmlunit.html.HTMLParser.parseHtml(HTMLParser.java:304)
at com.gargoylesoftware.htmlunit.DefaultPageCreator.createHtmlPage(DefaultPageCreator.java:134)
at com.gargoylesoftware.htmlunit.DefaultPageCreator.createPage(DefaultPageCreator.java:101)
at com.gargoylesoftware.htmlunit.WebClient.loadWebResponseInto(WebClient.java:420)
at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:303)
at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:360)
at org.openqa.selenium.htmlunit.HtmlUnitDriver.get(HtmlUnitDriver.java:228)
at org.openqa.selenium.htmlunit.HtmlUnitDriver.get(HtmlUnitDriver.java:216)
at org.openqa.selenium.internal.seleniumemulation.Open.handleSeleneseCommand(Open.java:36)
at org.openqa.selenium.internal.seleniumemulation.Open.handleSeleneseCommand(Open.java:22)
at org.openqa.selenium.internal.seleniumemulation.SeleneseCommand.apply(SeleneseCommand.java:33)
at Action.runSeleniumAction(Action.java:235)
at SessionDriver.runSession(SessionDriver.java:192)
at SessionDriver.run(SessionDriver.java:123)

---

没错，apply（）方法本身并没有引发该异常。apply（）方法中的其他内容是，打印完整的堆栈跟踪，而不是您决定的“fail”消息，这在某种程度上更好。

没错，apply（）方法本身不会引发该异常。apply method（）中的其他内容是，打印完整的堆栈跟踪而不是您决定的“fail”消息在某种程度上更好。

正如您在stacktrace中看到的，您的代码丢失了，因此您无法捕获异常。我猜

SessionDriver.run（）

是从另一个线程调用的

---

你试过了吗？它应该能够捕获这些错误并将它们传递给测试用例。

正如您在stacktrace中看到的，您的代码丢失了，因此您无法捕获异常。我猜

SessionDriver.run（）

是从另一个线程调用的

---

你试过了吗？它应该能够捕获这些错误并将它们传递给测试用例。

您使用的是eclipse-因此找到异常源的最简单方法是在调试模式下运行应用程序，并在

java.io.IOException

上设置断点。因此，每当在运行的VM中的某个地方抛出此异常时，eclipse都会停止应用程序并向您显示线程、类和代码行（如果可用）。

您正在使用eclipse-因此，找到异常源的最简单方法是在调试模式下运行应用程序，并在

java.io.IOException

上设置断点。因此，每当在运行的VM中的某个地方抛出此异常时，eclipse将停止应用程序并向您显示线程、类和代码行（如果可用）。

apply（）方法完全处理该异常，并且不会重新抛出它。如果它这样做了，它将被标记为“public void apply（）抛出IOException”

编译器会警告您这一点，因为如果不这样做，将导致错误处理不准确。

apply（）方法会完全处理异常，并且不会重新引发异常。如果它这样做了，它将被标记为“public void apply（）抛出IOException”

编译器会警告您这一点，因为如果不这样做，将导致错误处理不准确

java.io.IOException: Unable to download JavaScript from 'somesite' (status 404).
at com.gargoylesoftware.htmlunit.html.HtmlPage.loadJavaScriptFromUrl(HtmlPage.java:1023)
at com.gargoylesoftware.htmlunit.html.HtmlPage.loadExternalJavaScriptFile(HtmlPage.java:967)
at com.gargoylesoftware.htmlunit.html.HtmlScript.executeScriptIfNeeded(HtmlScript.java:353)
at com.gargoylesoftware.htmlunit.html.HtmlScript$1.execute(HtmlScript.java:225)
at com.gargoylesoftware.htmlunit.html.HtmlScript.onAllChildrenAddedToPage(HtmlScript.java:235)
at com.gargoylesoftware.htmlunit.html.HTMLParser$HtmlUnitDOMBuilder.endElement(HTMLParser.java:718)
at org.apache.xerces.parsers.AbstractSAXParser.endElement(Unknown Source)
at com.gargoylesoftware.htmlunit.html.HTMLParser$HtmlUnitDOMBuilder.endElement(HTMLParser.java:676)
at org.cyberneko.html.HTMLTagBalancer.callEndElement(HTMLTagBalancer.java:1136)
at org.cyberneko.html.HTMLTagBalancer.endElement(HTMLTagBalancer.java:1038)
at org.cyberneko.html.filters.DefaultFilter.endElement(DefaultFilter.java:206)
at org.cyberneko.html.filters.NamespaceBinder.endElement(NamespaceBinder.java:329)
at org.cyberneko.html.HTMLScanner$ContentScanner.scanEndElement(HTMLScanner.java:2999)
at org.cyberneko.html.HTMLScanner$ContentScanner.scan(HTMLScanner.java:1991)
at org.cyberneko.html.HTMLScanner.scanDocument(HTMLScanner.java:895)
at org.cyberneko.html.HTMLConfiguration.parse(HTMLConfiguration.java:499)
at org.cyberneko.html.HTMLConfiguration.parse(HTMLConfiguration.java:452)
at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
at com.gargoylesoftware.htmlunit.html.HTMLParser$HtmlUnitDOMBuilder.parse(HTMLParser.java:896)
at com.gargoylesoftware.htmlunit.html.HTMLParser.parse(HTMLParser.java:350)
at com.gargoylesoftware.htmlunit.html.HTMLParser.parseHtml(HTMLParser.java:304)
at com.gargoylesoftware.htmlunit.DefaultPageCreator.createHtmlPage(DefaultPageCreator.java:134)
at com.gargoylesoftware.htmlunit.DefaultPageCreator.createPage(DefaultPageCreator.java:101)
at com.gargoylesoftware.htmlunit.WebClient.loadWebResponseInto(WebClient.java:420)
at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:303)
at com.gargoylesoftware.htmlunit.WebClient.getPage(WebClient.java:360)
at org.openqa.selenium.htmlunit.HtmlUnitDriver.get(HtmlUnitDriver.java:228)
at org.openqa.selenium.htmlunit.HtmlUnitDriver.get(HtmlUnitDriver.java:216)
at org.openqa.selenium.internal.seleniumemulation.Open.handleSeleneseCommand(Open.java:36)
at org.openqa.selenium.internal.seleniumemulation.Open.handleSeleneseCommand(Open.java:22)
at org.openqa.selenium.internal.seleniumemulation.SeleneseCommand.apply(SeleneseCommand.java:33)
at Action.runSeleniumAction(Action.java:235)
at SessionDriver.runSession(SessionDriver.java:192)
at SessionDriver.run(SessionDriver.java:123)