springBoot中新建拦截器

最近项目中需要将请求中的header中增加几个字段，第一反应就是可不可以用拦截器拦截请求后将字段放进请求头中，经过网上一番学习后发现该方案可行，故将此方法记录下来供大家参考，也算是对自己学习成果的一个沉淀。

首先建一个拦截器类

package com.chwtest.filter;

import java.io.IOException;
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.annotation.WebFilter;

@WebFilter(filterName = "testFilter", urlPatterns = { "/testFilter" })
public class RequestFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        Filter.super.init(filterConfig);
    }

    @Override
    public void destroy() {
        Filter.super.destroy();
    }

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

        System.out.println("拦截器生效");
        chain.doFilter(request, response);
    }

}

该类需要一个注解：@WebFilter ，并且需要实现 Filter 并重写doFilter方法

在启动类中增加注解：@ServletComponentScan

package com.chwtest;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletComponentScan;

@SpringBootApplication
@ServletComponentScan
@EnableAutoConfiguration
public class App {
    public static void main(String[] args) {
        SpringApplication.run(App.class, args);
    }
}

新建一个controller

package com.chwtest.controller;

import javax.servlet.http.HttpServletRequest;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class Controller {
    @RequestMapping("testFilter")
    public String testFilter(HttpServletRequest request) {        
        return "hello word!";
    }

}

启动程序
至此拦截器已建好！
接下来是如何新增请求头字段
建一个RequestWrapper 继承HttpServletRequestWrapper，并重写父类方法

package com.chwtest.filter;

import java.util.Arrays;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

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

public class RequestWrapper extends HttpServletRequestWrapper {
    public RequestWrapper(HttpServletRequest request) {
        super(request);
    }

    private Map<String, String> headerMap = new HashMap<>();

    public void addHeader(String name, String value) {
        headerMap.put(name, value);
    }

    @Override
    public String getHeader(String name) {
        String headerValue = super.getHeader(name);
        if (headerMap.containsKey(name)) {
            headerValue = headerMap.get(name);
        }
        return headerValue;
    }

    @Override
    public Enumeration<String> getHeaders(String name) {
        List<String> values = Collections.list(super.getHeaders(name));
        if (headerMap.containsKey(name)) {
            values = Arrays.asList(headerMap.get(name));
        }
        return Collections.enumeration(values);
    }

    @Override
    public Enumeration<String> getHeaderNames() {
        List<String> names = Collections.list(super.getHeaderNames());
        for (String name : headerMap.keySet()) {
            names.add(name);
        }
        return Collections.enumeration(names);
    }

    @Override
    public int getIntHeader(String name) {
        return super.getIntHeader(name);
    }
}

filter中将heaer赋值

package com.chwtest.filter;
 
import java.io.IOException;
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.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
 
@WebFilter(filterName = "testFilter", urlPatterns = { "/testFilter" })
public class RequestFilter implements Filter {
 
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        Filter.super.init(filterConfig);
    }
 
    @Override
    public void destroy() {
        Filter.super.destroy();
    }
 
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest) request;
        RequestWrapper requestMapper = new RequestWrapper(req);
        requestMapper.addHeader("name", "陈浩文");
        System.out.println("拦截器生效");
        chain.doFilter(requestMapper, response);
    }
 
}