spring cloud zuul过滤器修改requestURI 忽略大小写

通过zuul网关处理requestURI可以做很多事情，如对uri的解密，转发，大小写转化等。

这里对URI做一个简单的大小写的转化。

写一个filter实现ZuulFilter:

package com.cis.mr.audit.config;

import com.netflix.zuul.ZuulFilter;
import com.netflix.zuul.context.RequestContext;
import com.netflix.zuul.exception.ZuulException;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

import static org.springframework.cloud.netflix.zuul.filters.support.FilterConstants.PRE_TYPE;

/**
 * @author ：hkk
 * @date ：Created in 2019/7/11 9:45
 */

public class CaseInsenistiveFilter extends ZuulFilter {
    @Override
    public String filterType() {
        return PRE_TYPE;
    }

    @Override
    public int filterOrder() {
        return 4;
    }

    @Override
    public boolean shouldFilter() {
        return true;
    }

    @Override
    public Object run() throws ZuulException {
        RequestContext ctx = RequestContext.getCurrentContext();
        HttpServletRequest request = ctx.getRequest();
        String requestURI = request.getRequestURI();

        HttpServletRequestWrapper requestWrapper = new HttpServletRequestWrapper(request){
            @Override
            public String getRequestURI() {
                return requestURI.toLowerCase();
            }
        };

        ctx.setRequest(requestWrapper);

        return null;
    }
}

注意这里有几点：

1. filterType是PRE_TYPE ，这是zuul定义的常量。可以通过FilterConstants查看。PRE_TYPE如下图，表示在处理转发请求之前的操作。

2. flterOrder是4,为什么是4,这里要了解zuul几个自带的filter。特别是PreDecorationFilter

下面是几个常用filter的order:

    /**
     * Filter Order for {@link DebugFilter#filterOrder()}.
     */
    public static final int DEBUG_FILTER_ORDER = 1;

    /**
     * Filter Order for
     * {@link org.springframework.cloud.netflix.zuul.filters.pre.FormBodyWrapperFilter#filterOrder()}.
     */
    public static final int FORM_BODY_WRAPPER_FILTER_ORDER = -1;

    /**
     * Filter Order for
     * {@link org.springframework.cloud.netflix.zuul.filters.pre.PreDecorationFilter}.
     */
    public static final int PRE_DECORATION_FILTER_ORDER = 5;

    /**
     * Filter Order for
     * {@link org.springframework.cloud.netflix.zuul.filters.route.RibbonRoutingFilter#filterOrder()}.
     */
    public static final int RIBBON_ROUTING_FILTER_ORDER = 10;

    /**
     * Filter Order for
     * {@link org.springframework.cloud.netflix.zuul.filters.post.SendErrorFilter#filterOrder()}.
     */
    public static final int SEND_ERROR_FILTER_ORDER = 0;

    /**
     * Filter Order for {@link SendForwardFilter#filterOrder()}.
     */
    public static final int SEND_FORWARD_FILTER_ORDER = 500;

    /**
     * Filter Order for
     * {@link org.springframework.cloud.netflix.zuul.filters.post.SendResponseFilter#filterOrder()}.
     */
    public static final int SEND_RESPONSE_FILTER_ORDER = 1000;

    /**
     * Filter Order for
     * {@link org.springframework.cloud.netflix.zuul.filters.route.SimpleHostRoutingFilter#filterOrder()}.
     */
    public static final int SIMPLE_HOST_ROUTING_FILTER_ORDER = 100;

    /**
     * filter order for {@link Servlet30WrapperFilter#filterOrder()}.
     */
    public static final int SERVLET_30_WRAPPER_FILTER_ORDER = -2;

    /**
     * filter order for
     * {@link org.springframework.cloud.netflix.zuul.filters.pre.ServletDetectionFilter#filterOrder()}.
     */
    public static final int SERVLET_DETECTION_FILTER_ORDER = -3;

可以看到PreDecorationFilter的order是5,在它之前的filter，我们设置一个getRequestURI的值，就可以实现需求，PreDecorationFilter是zuul很重要的过滤器，推荐大家仔细了解一下。

最后，我们注入这上fitler。

@Bean
    public CaseInsenistiveFilter getCaseFilter() {
        return new CaseInsenistiveFilter();
    }