缺少servlet api 3.0 jar中的異步方法？

Question

我正在開發一個servlet 3.0應用程序，它必須異步處理請求。

編譯失敗了

cannot find symbol
symbol  : method startAsync(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)
location: interface javax.servlet.http.HttpServletRequest

信息。

我的pom.xml中有以下依賴項：

<dependency>
    <groupId>javax</groupId>
    <artifactId>javaee-web-api</artifactId>
    <version>6.0</version>
</dependency>

有趣的是， 導入javax.servlet.AsyncContext成功。 但是當我列出javax.servlet.ServletRequest的方法時，3.0 API中沒有處理異步請求的方法。

public abstract java.lang.String javax.servlet.ServletRequest.getScheme()
public abstract java.lang.String javax.servlet.ServletRequest.getProtocol()
public abstract javax.servlet.ServletInputStream javax.servlet.ServletRequest.getInputStream() throws java.io.IOException
public abstract int javax.servlet.ServletRequest.getContentLength()
public abstract java.lang.Object javax.servlet.ServletRequest.getAttribute(java.lang.String)
public abstract java.lang.String javax.servlet.ServletRequest.getContentType()
public abstract java.util.Locale javax.servlet.ServletRequest.getLocale()
public abstract java.util.Enumeration javax.servlet.ServletRequest.getAttributeNames()
public abstract java.lang.String javax.servlet.ServletRequest.getCharacterEncoding()
public abstract void javax.servlet.ServletRequest.setCharacterEncoding(java.lang.String) throws java.io.UnsupportedEncodingException
public abstract java.lang.String javax.servlet.ServletRequest.getParameter(java.lang.String)
public abstract java.util.Enumeration javax.servlet.ServletRequest.getParameterNames()
public abstract java.lang.String[] javax.servlet.ServletRequest.getParameterValues(java.lang.String)
public abstract java.util.Map javax.servlet.ServletRequest.getParameterMap()
public abstract java.lang.String javax.servlet.ServletRequest.getServerName()
public abstract int javax.servlet.ServletRequest.getServerPort()
public abstract java.io.BufferedReader javax.servlet.ServletRequest.getReader() throws java.io.IOException
public abstract java.lang.String javax.servlet.ServletRequest.getRemoteAddr()
public abstract java.lang.String javax.servlet.ServletRequest.getRemoteHost()
public abstract void javax.servlet.ServletRequest.setAttribute(java.lang.String,java.lang.Object)
public abstract void javax.servlet.ServletRequest.removeAttribute(java.lang.String)
public abstract java.util.Enumeration javax.servlet.ServletRequest.getLocales()
public abstract boolean javax.servlet.ServletRequest.isSecure()
public abstract javax.servlet.RequestDispatcher javax.servlet.ServletRequest.getRequestDispatcher(java.lang.String)
public abstract java.lang.String javax.servlet.ServletRequest.getRealPath(java.lang.String)
public abstract int javax.servlet.ServletRequest.getRemotePort()
public abstract java.lang.String javax.servlet.ServletRequest.getLocalName()
public abstract java.lang.String javax.servlet.ServletRequest.getLocalAddr()
public abstract int javax.servlet.ServletRequest.getLocalPort()

我錯過了什么？

Answer 1

我假設你以某種方式“管理”引用了一個舊的servlet-api庫（可能是傳遞的），它位於javaee-web-api之前的類路徑中。 這意味着現有的類是從舊的servlet-api中獲取的，而舊版本中不存在的類是從javaee-web-api加載的。

您可以運行mvn dependency:tree來查看引用過時庫的位置，然后將其排除。