[Java知识库]springboot http代理 手动注册多个servlet

java的http代理已经存在可以直接使用的库, smiley-http-proxy-servlet,原理就是copy请求,进行转发
需求有点类似网关的功能,就是对请求进行前置与后置处理,不想引入springcloud与springgateway,所以就需要对smiley-http-proxy-servlet做一些封装
a. 主要是需要手动注册多个servlet,监听一些请求,
b. Servlet在执行service方法时,可改写请求参数
c. Servlet在执行service方法后, 对servletRequest与servletResponse进行copy,
d. 做一些业务处理

1. 引入smiley-http-proxy-servlet库
   pom.xml

        <dependency>
            <groupId>org.mitre.dsmiley.httpproxy</groupId>
            <artifactId>smiley-http-proxy-servlet</artifactId>
            <version>1.12.1</version>
        </dependency>

2. 配置监听的请求和转发的请求,
   application.yml

proxy:
  configs:
    - servlet_url: /proxy/*
      target_url: http://192.168.0.4:8401/handler1
#      logging_enabled: false
    - servlet_url: /proxy_1/*
      target_url: http://192.168.0.141:9004/handler
      logging_enabled: true

    - servlet_url: /proxy_2/*
      target_url: http://192.168.0.141:8400/handler2
      logging_enabled: true

3. 配置类

@Data
@ConfigurationProperties(prefix = "proxy")
@Component
public class ProxyConfig {
    private List<ProxyProperties> configs;
    @Data
    public static class ProxyProperties {
        private String servletUrl;
        private String targetUrl;
        private Boolean loggingEnabled =false;
    }

}

4. springboot 代码形式手动注册servlet

@Component
public class ServletConfig implements ServletContextInitializer{
    private final ProxyConfig config;
    @Autowired
    public ServletConfig(ProxyConfig config){
        this.config = config;
    }
    @Override
    public void onStartup(ServletContext servletContext) {
        List<ProxyConfig.ProxyProperties> propertiesList = config.getConfigs();
        for (int i = 0; i < propertiesList.size(); i++) {
            ProxyConfig.ProxyProperties properties = propertiesList.get(i);
            //定义多个servlet
            ServletRegistration initServlet = servletContext.addServlet("MyProxyServlet"+i, MyProxyServlet.class);
            initServlet.addMapping(properties.getServletUrl());
            initServlet.setInitParameter(ProxyServlet.P_TARGET_URI, properties.getTargetUrl());
            initServlet.setInitParameter(ProxyServlet.P_LOG, properties.getLoggingEnabled().toString());
        }
    }
}

5. 重写servlet, 获取请求,与结果,对其进行一些记录,或者

public class MyProxyServlet extends ProxyServlet {

    private SourceController biddingController;
	//重写servlet, 获取servletRequest与servletResponse
    protected void service(HttpServletRequest servletRequest, HttpServletResponse servletResponse) throws ServletException, IOException {
        MyHttpServletRequestWrapper requestWrapper = new MyHttpServletRequestWrapper(servletRequest);
        byte[] res = serviceV1(super.targetUri,requestWrapper,servletResponse);//改写请求参数
        this.doExtend(requestWrapper,res);//获取到rep与resp后,去业务处理
        略....
    }

}

6. 重写ServletRequest类

public class MyHttpServletRequestWrapper extends HttpServletRequestWrapper {
	...略
}

7. 获取请求返回的结果,
   使用smiley-http-proxy-servlet的ProxyServlet::copyResponseEntity方法即可