java – 如何外化web.xml servlet init-param？ Servlets的Spring DelegatingFilterProxy？

我有一个我无法修改的第三方servlet.它接受我想要外化的init-param(来自web.xml).

我可以使用DelegatingFilterProxy外化servlet过滤器init-param.这有效地将servlet过滤器定义移动到Spring中,其中有更强大的外化工具(例如：PropertyPlaceholderConfigurer,环境变量等)

我怎样才能为servlet做这个？

最佳答案

看起来你需要一个DelegatingServletProxy类,虽然这在Spring中不存在但是,我认为编码非常简单,使用DelegatingFilterProxy作为起点.

servlet只实现了一些具体的方法,因此委托应该是直截了当的.

好吧,我把钱放在嘴边！
编辑：下面是DelegatingServletProxy的基本实现.

你这样使用它：

>在web.xml中设置常用的spring上下文配置/ ContextListener,为webapp设置应用程序范围的spring上下文.
>将servlet添加到web.xml,其实现类为DelegatingServletProxy.这将取代您想要更改init-params的现有serlvet.为这个新的servlet设置init参数：proxyServletClass是servlet类的名称. proxyServletParams是spring配置中的Properties bean的名称.此属性bean用于为代理的servlet设置init参数.
>在spring配置中,添加一个定义init-params的新Properites bean

一些示例,在spring应用程序上下文中


示例web.xml代码段


这是servlet代码,它很长,但大多数是委托ServletContext  – 有趣的东西发生在顶部.它未经测试 – 应该被视为一个起点.

import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

import javax.servlet.*;
import javax.servlet.http.HttpServlet;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Enumeration;
import java.util.Properties;
import java.util.Set;

public class DelegatingServletProxy extends HttpServlet implements WebApplicationContextAware
{
    private HttpServlet delegate;

    private Properties initParams;
    private String delegateName;

    public void setDelegateName(String delegateName)
    {
        this.delegateName = delegateName;
    }

    public void init(ServletConfig config) throws ServletException
    {
        super.init(config);
        WebApplicationContext wac = WebApplicationContextUtils.getrequiredWebApplicationContext(getServletContext());
        delegate = wac.getBean(delegateName,HttpServlet.class);
        delegate.init(new WrapServletConfig(config));
    }

    @Override
    public void destroy()
    {
        delegate.destroy();
    }

    @Override
    public void service(ServletRequest req,ServletResponse res) throws ServletException,IOException
    {
        delegate.service(req,res);
    }

    public void setInitParams(Properties initParams)
    {
        this.initParams = initParams;
    }

    private class WrapServletConfig implements ServletConfig,ServletContext
    {
        // we override ServletContext also because it exposes getInitParameterNames()/getInitParemter()
        private ServletConfig delegate;
        private ServletContext delegateContext;
        public WrapServletConfig(ServletConfig config)
        {
            this.delegate = config;
            this.delegateContext = config.getServletContext();
        }

        @Override
        public String getServletName()
        {
            return delegate.getServletName();
        }

        @Override
        public ServletContext getServletContext()
        {
            return delegate.getServletContext();
        }

        @Override
        public String getInitParameter(String s)
        {
            return initParams.getProperty(s);
        }

        @Override
        public Enumeration getInitParameterNames()
        {
            return initParams.propertyNames();
        }

        @Override
        public Object getAttribute(String s)
        {
            return delegateContext.getAttribute(s);
        }

        @Override
        public Enumeration getAttributeNames()
        {
            return delegateContext.getAttributeNames();
        }

        @Override
        public void setAttribute(String s,Object o)
        {
            delegateContext.setAttribute(s,o);
        }

        @Override
        public void removeAttribute(String s)
        {
            delegateContext.removeAttribute(s);
        }

        @Override
        public String getServletContextName()
        {
            return delegateContext.getServletContextName();
        }

        // the remainer is just straight delegation to ServletContext

        @Override
        public ServletContext getContext(String s)
        {
            return delegateContext.getContext(s);
        }

        @Override
        public int getMajorVersion()
        {
            return delegateContext.getMajorVersion();
        }

        @Override
        public int getMinorVersion()
        {
            return delegateContext.getMinorVersion();
        }

        @Override
        public String getMimeType(String s)
        {
            return delegateContext.getMimeType(s);
        }

        @Override
        public Set getResourcePaths(String s)
        {
            return delegateContext.getResourcePaths(s);
        }

        @Override
        public URL getResource(String s)
                throws MalformedURLException
        {
            return delegateContext.getResource(s);
        }

        @Override
        public InputStream getResourceAsStream(String s)
        {
            return delegateContext.getResourceAsStream(s);
        }

        @Override
        public RequestDispatcher getRequestDispatcher(String s)
        {
            return delegateContext.getRequestDispatcher(s);
        }

        @Override
        public RequestDispatcher getNamedDispatcher(String s)
        {
            return delegateContext.getNamedDispatcher(s);
        }

        @Override
        public Servlet getServlet(String s)
                throws ServletException
        {
            return delegateContext.getServlet(s);
        }

        @Override
        public Enumeration getServlets()
        {
            return delegateContext.getServlets();
        }

        @Override
        public Enumeration getServletNames()
        {
            return delegateContext.getServletNames();
        }

        @Override
        public void log(String s)
        {
            delegateContext.log(s);
        }

        @Override
        public void log(Exception e,String s)
        {
            delegateContext.log(e,s);
        }

        @Override
        public void log(String s,Throwable throwable)
        {
            delegateContext.log(s,throwable);
        }

        @Override
        public String getRealPath(String s)
        {
            return delegateContext.getRealPath(s);
        }

        @Override
        public String getServerInfo()
        {
            return delegateContext.getServerInfo();
        }
    }
}


 原文链接：https://www.f2er.com/spring/432699.html

java – 如何外化web.xml servlet init-param？ Servlets的Spring DelegatingFilterProxy？

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