小贝子编程

使用getServlet上下文().getRealPath()在筛选器中加载图像



过滤器中的此String：

   String duke = request.getServletContext().getRealPath("") + "\" + "duke.gif";

是或应该是指向duke.gif的路径。如何使duke加载图像？假设图像被移动到WEB-INF/IMAGES/duke.gif？

此外，这是在JSP中加载图像的合理方法吗？我想在过滤器代码中动态加载图像。对于这个duke的例子，它总是相同的gif，但我希望能够在过滤器中更改它。

我使用的是Netbeans和Linux，但希望它是可移植的。

此JSP:

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>login</title>
    </head>
    <body>
        <img src="${requestScope.duke}"> 
        ${requestScope.me}, what's yours?
        <form name="user_name_form" action="controller" method="POST">
            name <input type="text" name="name" value="skinner" size='20' />
            <p>
                <input type="submit">
            </p>
        </form>
        ${requestScope.message}
        <img src="${pageContext.request.contextPath}/WEB-INF/IMAGES/duke.gif" />
        <img src="/WEB-INF/IMAGES/duke.gif" />
        <img src="http://localhost:8080/WebApplication/WEB-INF/IMAGES/duke.gif" />
    </body>
</html>

结果在这个html:

<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>login</title>
    </head>
    <body>
        <img src="WEB-INF/IMAGES/duke.gif"> 
        my name is thufir 34562345, what's yours?
        <form name="user_name_form" action="controller" method="POST">
            name <input type="text" name="name" value="skinner" size='20' />
            <p>
                <input type="submit">
            </p>
        </form>
        <img src="/WebApplication/WEB-INF/IMAGES/duke.gif" />
        <img src="/WEB-INF/IMAGES/duke.gif" />
        <img src="http://localhost:8080/WebApplication/WEB-INF/IMAGES/duke.gif" />
    </body>
</html>

过滤器：

package net.bounceme.dur.filter;
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.logging.Logger;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class AuthenticateFilter implements Filter {
    private static final Logger log = Logger.getLogger(AuthenticateFilter.class.getName());
    private FilterConfig filterConfig = null;
    private Map<String, String> mapOfUsers = new HashMap<>();
    public AuthenticateFilter() {
    }
    private void doBeforeProcessing(ServletRequest request, ServletResponse response) throws IOException, ServletException {
        log.fine("do before processing..");
    }
    private void doAfterProcessing(ServletRequest request, ServletResponse response) throws IOException, ServletException {
        log.fine("do after processing");  //add image here?
    }
    private void makeMap() {
        Enumeration<String> parmNamesEnum = filterConfig.getInitParameterNames();
        List<String> keys = Collections.list(parmNamesEnum);
        for (String s : keys) {
            mapOfUsers.put(s, filterConfig.getInitParameter(s));
        }
        log.fine(mapOfUsers.toString());
    }
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        log.fine("do filter");
        HttpServletRequest req = (HttpServletRequest) request;
        HttpServletResponse res = (HttpServletResponse) response;
        String uri = req.getRequestURI();
        log.fine("Requested Resource::" + uri);
        makeMap();  //debatable  and maybe should be in init?  only should run once.
        String name = (String) request.getAttribute("name");
        String message = mapOfUsers.containsValue(name) ? "hello " + name : "no " + name;
        String myName = request.getServletContext().getInitParameter("me");
        String myId = request.getServletContext().getInitParameter("id");
        String me = "my name is " + myName + " " + myId;
        boolean authenticated = mapOfUsers.containsValue(name) ? true : false;
        message = authenticated ? "hello " + name : "";
        //   String duke = request.getServletContext().getRealPath("//duke.gif");
        String duke = request.getServletContext().getRealPath("") + "\" + "duke.gif";
        duke = "WEB-INF/IMAGES/duke.gif";
        log.info("filter user isttt" + message);
        log.info("filter authenticated istt" + authenticated);
        log.info("filter message istt" + message);
        log.info("filter duke isttt" + duke);
        request.setAttribute("me", me);
        request.setAttribute("authenticated", authenticated);
        request.setAttribute("message", message);
        request.setAttribute("duke", duke);
        chain.doFilter(request, response);
    }
    public FilterConfig getFilterConfig() {
        return (this.filterConfig);
    }
    public void setFilterConfig(FilterConfig filterConfig) {
        this.filterConfig = filterConfig;
    }
    @Override
    public void destroy() {
    }
    @Override
    public void init(FilterConfig filterConfig) {
        log.fine("init");
        this.filterConfig = filterConfig;
        if (filterConfig != null) {
            log.fine("SessionCheckFilter:Initializing filter");
        } else {
            log.warning("null filterConfig");
        }
    }
    @Override
    public String toString() {
        if (filterConfig == null) {
            return ("SessionCheckFilter()");
        }
        StringBuilder sb = new StringBuilder("SessionCheckFilter(");
        sb.append(filterConfig);
        sb.append(")");
        return (sb.toString());
    }
    private void sendProcessingError(Throwable t, ServletResponse response) {
        log.fine("send processing error");
        String stackTrace = getStackTrace(t);
        if (stackTrace != null && !stackTrace.equals("")) {
            try {
                response.setContentType("text/html");
                try (PrintStream ps = new PrintStream(response.getOutputStream()); PrintWriter pw = new PrintWriter(ps)) {
                    pw.print("<html>n<head>n<title>Error</title>n</head>n<body>n"); //NOI18N
                    pw.print("<h1>The resource did not process correctly</h1>n<pre>n");
                    pw.print(stackTrace);
                    pw.print("</pre></body>n</html>"); //NOI18N
                }
                response.getOutputStream().close();
            } catch (Exception ex) {
            }
        } else {
            try {
                try (PrintStream ps = new PrintStream(response.getOutputStream())) {
                    t.printStackTrace(ps);
                }
                response.getOutputStream().close();
            } catch (Exception ex) {
            }
        }
    }
    public static String getStackTrace(Throwable t) {
        String stackTrace = null;
        try {
            StringWriter sw = new StringWriter();
            PrintWriter pw = new PrintWriter(sw);
            t.printStackTrace(pw);
            pw.close();
            sw.close();
            stackTrace = sw.getBuffer().toString();
        } catch (Exception ex) {
        }
        log.warning(stackTrace);
        return stackTrace;
    }
}

另请参阅：

https://askubuntu.com/questions/583309/when-a-war-is-deployed-in-glassfish-whats-the-path-to-web-inf

您似乎正在将"磁盘上"的位置而不是url返回到图像中，这在某种程度上取决于servlet在应用程序服务器中的配置方式，但我猜，仅调用"images/duk.gif"就足以加载图像。

这种拼凑有效。

战争文件：

thufir@doge:~$ 
thufir@doge:~$ jar -tf NetBeansProjects/WebApplication/dist/WebApplication.war 
META-INF/
META-INF/MANIFEST.MF
WEB-INF/
WEB-INF/classes/
WEB-INF/classes/beginnersbook/
WEB-INF/classes/beginnersbook/com/
WEB-INF/classes/net/
WEB-INF/classes/net/bounceme/
WEB-INF/classes/net/bounceme/dur/
WEB-INF/classes/net/bounceme/dur/filter/
WEB-INF/classes/net/bounceme/dur/servlets/
WEB-INF/images/
WEB-INF/resources/
WEB-INF/classes/beginnersbook/com/Details.class
WEB-INF/classes/net/bounceme/dur/filter/AuthenticateFilter.class
WEB-INF/classes/net/bounceme/dur/filter/SessionCheckFilter.class
WEB-INF/classes/net/bounceme/dur/servlets/Controller.class
WEB-INF/classes/net/bounceme/dur/servlets/MyToken.class
WEB-INF/classes/properties.properties
WEB-INF/duke.gif
WEB-INF/fail.jsp
WEB-INF/images/duke.gif
WEB-INF/login.jsp
WEB-INF/resources/duke.gif
WEB-INF/success.jsp
WEB-INF/web.xml
duke.gif
index.html
thufir@doge:~$

html（duke图像加载）:

<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>login</title>
    </head>
    <body>
        <img src="http://localhost:8080/WebApplication/duke.gif"> 
        my name is thufir 34562345, what's yours?
        <form name="user_name_form" action="controller" method="POST">
            name <input type="text" name="name" value="skinner" size='20' />
            <p>
                <input type="submit">
            </p>
        </form>
    </body>
</html>

login.jsp代码：

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>login</title>
    </head>
    <body>
        <img src="${requestScope.duke}"> 
        ${requestScope.me}, what's yours?
        <form name="user_name_form" action="controller" method="POST">
            name <input type="text" name="name" value="skinner" size='20' />
            <p>
                <input type="submit">
            </p>
        </form>
        ${requestScope.message}
    </body>
</html>

和过滤器：

package net.bounceme.dur.filter;
import java.io.IOException;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.logging.Logger;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class AuthenticateFilter implements Filter {
    private static final Logger log = Logger.getLogger(AuthenticateFilter.class.getName());
    private FilterConfig filterConfig = null;
    private Map<String, String> mapOfUsers = new HashMap<>();
    public AuthenticateFilter() {
    }
    private void doBeforeProcessing(ServletRequest request, ServletResponse response) throws IOException, ServletException {
        log.fine("do before processing..");
    }
    private void doAfterProcessing(ServletRequest request, ServletResponse response) throws IOException, ServletException {
        log.fine("do after processing");  //add image here?
    }
    private void makeMap() {
        Enumeration<String> parmNamesEnum = filterConfig.getInitParameterNames();
        List<String> keys = Collections.list(parmNamesEnum);
        for (String s : keys) {
            mapOfUsers.put(s, filterConfig.getInitParameter(s));
        }
        log.fine(mapOfUsers.toString());
    }
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        log.fine("do filter");
        HttpServletRequest req = (HttpServletRequest) request;
        HttpServletResponse res = (HttpServletResponse) response;
        String uri = req.getRequestURI();
        log.fine("Requested Resource::" + uri);
        makeMap();  //debatable  and maybe should be in init?  only should run once.
        String name = (String) request.getAttribute("name");
        String message = mapOfUsers.containsValue(name) ? "hello " + name : "no " + name;
        String myName = request.getServletContext().getInitParameter("me");
        String myId = request.getServletContext().getInitParameter("id");
        String me = "my name is " + myName + " " + myId;
        boolean authenticated = mapOfUsers.containsValue(name) ? true : false;
        message = authenticated ? "hello " + name : "";
        String hp = request.getServerName();
        int p = request.getServerPort();
        String duke = "http://" + hp + ":" + p + request.getServletContext().getContextPath() + "/duke.gif";
        log.info("filter user isttt" + message);
        log.info("filter authenticated istt" + authenticated);
        log.info("filter message istt" + message);
        log.info("filter duke isttt" + duke);
        request.setAttribute("me", me);
        request.setAttribute("authenticated", authenticated);
        request.setAttribute("message", message);
        request.setAttribute("duke", duke);
        chain.doFilter(request, response);
    }
    public FilterConfig getFilterConfig() {
        return (this.filterConfig);
    }
    public void setFilterConfig(FilterConfig filterConfig) {
        this.filterConfig = filterConfig;
    }
    @Override
    public void destroy() {
    }
    @Override
    public void init(FilterConfig filterConfig) {
        log.fine("init");
        this.filterConfig = filterConfig;
        if (filterConfig != null) {
            log.fine("SessionCheckFilter:Initializing filter");
        } else {
            log.warning("null filterConfig");
        }
    }
    @Override
    public String toString() {
        if (filterConfig == null) {
            return ("SessionCheckFilter()");
        }
        StringBuilder sb = new StringBuilder("SessionCheckFilter(");
        sb.append(filterConfig);
        sb.append(")");
        return (sb.toString());
    }
    private void sendProcessingError(Throwable t, ServletResponse response) {
        log.fine("send processing error");
        String stackTrace = getStackTrace(t);
        if (stackTrace != null && !stackTrace.equals("")) {
            try {
                response.setContentType("text/html");
                try (PrintStream ps = new PrintStream(response.getOutputStream()); PrintWriter pw = new PrintWriter(ps)) {
                    pw.print("<html>n<head>n<title>Error</title>n</head>n<body>n"); //NOI18N
                    pw.print("<h1>The resource did not process correctly</h1>n<pre>n");
                    pw.print(stackTrace);
                    pw.print("</pre></body>n</html>"); //NOI18N
                }
                response.getOutputStream().close();
            } catch (Exception ex) {
            }
        } else {
            try {
                try (PrintStream ps = new PrintStream(response.getOutputStream())) {
                    t.printStackTrace(ps);
                }
                response.getOutputStream().close();
            } catch (Exception ex) {
            }
        }
    }
    public static String getStackTrace(Throwable t) {
        String stackTrace = null;
        try {
            StringWriter sw = new StringWriter();
            PrintWriter pw = new PrintWriter(sw);
            t.printStackTrace(pw);
            pw.close();
            sw.close();
            stackTrace = sw.getBuffer().toString();
        } catch (Exception ex) {
        }
        log.warning(stackTrace);
        return stackTrace;
    }
}

我相信还有更好的方法。

相关内容

最新更新


热门标签：

javascript python java c# php android html jquery c++ css ios sql mysql arrays asp.net json python-3.x ruby-on-rails .net sql-server django objective-c excel regex ruby linux ajax iphone xml vba spring asp.net-mvc database wordpress string postgresql wpf windows xcode bash git oracle list vb.net multithreading eclipse algorithm macos powershell visual-studio image forms numpy scala function api selenium