spring-boot应用程序
我的项目中没有ApplicationContext.xml或web.xml文件。我更喜欢避免它们，并使用Java代码配置所有内容。
我已经阅读了以下关于servlet过滤器中bean注入的文章。

1. How can I get a Spring bean in a servlet filter?
2. http://www.deadcoderising.com/2015-05-04-dependency-injection-into-filters-using-delegatingfilterproxy/
3. spring injection in servlet filter
   阅读完它们后，我开始使用DelegatingFilterProxy。
   我的问题是如何autowire到过滤器的bean，并避免使用xml文件，特别是对于DelegatingFilterProxy配置。
   代码片段可以从github.中的第二篇文章中获得。

public class AuditHandler {

    public void auditRequest(String appName, ServletRequest request) {
        System.out.println(appName + ": Received request from " + request.getRemoteAddr() );
    }
}

public class AuditFilter implements Filter {

    private final AuditHandler auditHandler;
    private String appName;

    public AuditFilter(AuditHandler auditHandler) {
        this.auditHandler = auditHandler;
    }

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {

        auditHandler.auditRequest(appName, request);
        chain.doFilter(request, response);
    }

    public void init(FilterConfig filterConfig) throws ServletException {
        appName = filterConfig.getInitParameter("appName");
    }

    public void destroy() {}
}

ApplicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
                           http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="auditHandler" class="com.deadcoderising.AuditHandler">
    </bean>

    <bean id="auditFilter" class="com.deadcoderising.AuditFilter">
        <constructor-arg ref="auditHandler"/>
    </bean>
</beans>

web.xml

<web-app version="3.0"
         xmlns="http://java.sun.com/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
         metadata-complete="true">

    <listener>
        <listener-class>
            org.springframework.web.context.ContextLoaderListener
        </listener-class>
    </listener>

    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath*:applicationContext*.xml</param-value>
    </context-param>

    <filter>
        <filter-name>auditFilter</filter-name>
        <filter-class>
            org.springframework.web.filter.DelegatingFilterProxy
        </filter-class>
        <init-param>
            <param-name>targetFilterLifecycle</param-name>
            <param-value>true</param-value>
        </init-param>
        <init-param>
            <param-name>appName</param-name>
            <param-value>di-example</param-value>
        </init-param>
    </filter>

    <filter-mapping>
        <filter-name>auditFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

</web-app>