Springboot实现Web组件注册

一、前言
在实际开发中，有时候我们可能使用springboot注册web组件，实现某些功能，比如我们需要生成一些api来提供对外的服务，而对应的路径其实是不固定的，那么这种情况下，其实是可以通过这种方式来注册web组件的。

二、如何实现？
1.使用SpringBoot注解加继承HttpServet类实现注册Servlet组件。

@WebServlet("/api")
public class APIServlet extends HttpServlet {
	@Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
        log.debug("servlet execute");
        String servletPath = request.getRequestURI();
        servletPath = servletPath.substring(apiContext.length() + 2);
        PrintWriter out = null;
        try {
            out = response.getWriter();
            ResponseDto responseDto = process(servletPath, request, response);
            out.append(JSON.toJSONString(responseDto));

        } catch (Exception e) {
            response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
            out.append(JSON.toJSONString(ResponseDto.fail(e.toString())));
            log.error(e.toString(), e);
        } finally {
            if (out != null)
                out.close();
        }
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        doGet(req, resp);
    }
    public ResponseDto process(String path, HttpServletRequest request, HttpServletResponse response) {
    System.out.println("请求处理");
    ResponseDto dto = new ResponseDto();
    return dto;
    }
}
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2.通过继承HttpServet类加配置类来进行注册。

public class APIServlet extends HttpServlet {
	@Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
        log.debug("servlet execute");
        String servletPath = request.getRequestURI();
        servletPath = servletPath.substring(apiContext.length() + 2);
        PrintWriter out = null;
        try {
            out = response.getWriter();
            ResponseDto responseDto = process(servletPath, request, response);
            out.append(JSON.toJSONString(responseDto));

        } catch (Exception e) {
            response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
            out.append(JSON.toJSONString(ResponseDto.fail(e.toString())));
            log.error(e.toString(), e);
        } finally {
            if (out != null)
                out.close();
        }
    }
}
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新建一个配置类，将该Servlet加载到Spring容器中，配置类代码如下：

@Slf4j
@Configuration
public class ServletConfig {
    @Value("${dbapi.api.context}")
    String apiContext;

    @Autowired
    private APIServlet apiServlet;


    @Bean
    public ServletRegistrationBean getServletRegistrationBean() {
        String format = String.format("/%s/*", apiContext);
        ServletRegistrationBean bean = new ServletRegistrationBean(apiServlet);
        bean.addUrlMappings(format);
        log.info("regist APIServlet servelet for {} urlMappings",format);
        return bean;
    }
}
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两种注册方式都是可用的。

3.注册Filter组件实现过滤。

@Slf4j
@Component
@WebFilter("/api")
public class ApiIPFilter implements Filter {

    @Autowired
    private IPService ipService;

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException {
        log.debug("IP filter execute");
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;

        String originIp = IPUtil.getOriginIp(request);

        String method = request.getMethod();
        PrintWriter out = null;
       try {

            //js跨域的预检请求，不经过处理逻辑。开发模式下，前端启动，访问8521的页面进行请求测试会跨域
            if (method.equals("OPTIONS")) {
                response.setStatus(HttpServletResponse.SC_OK);
                return;
            }

            boolean checkIP = ipService.checkIP(originIp);
            if (!checkIP) {
                out = response.getWriter();
                response.setStatus(HttpServletResponse.SC_FORBIDDEN);
                out.append(JSON.toJSONString(ResponseDto.fail("Illegal ip (" + originIp + "), access forbidden")));

            } else {
                filterChain.doFilter(servletRequest, servletResponse);
            }
        } catch (Exception e) {
            response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
            out.append(JSON.toJSONString(ResponseDto.fail(e.toString())));
            log.error(e.toString());

        } finally {
            if (out != null) {
                out.close();
            }
        }

    }
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这里会对某些IP进行过滤。

最后启动类中的@ServletComponentScan注解扫描web组件。

@SpringBootApplication
//SpringBoot启动时扫描注册注解标注的Web组件
@ServletComponentScan
public class SpringbootDemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringbootDemoApplication.class, args);
        
    }
}
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