Spring Boot 注册 Servlet 的五种方法(最新整理)_Java

在spring boot中注册servlet有几种方法，每种方法适用于不同的场景和需求。下面列出五种常见的方法：

一、spring boot 提供了 servletregistrationbean, filterregistrationbean, servletlistenerregistrationbean 三个类分别用来注册 servlet, filter, listener

import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import java.io.ioexception;
public class registerservlet extends httpservlet {
    @override
    protected void service(httpservletrequest req, httpservletresponse resp) throws ioexception {
        string name = getservletconfig().getinitparameter("name");
        string sex = getservletconfig().getinitparameter("sex");
        resp.getoutputstream().println("name is " + name);
        resp.getoutputstream().println("sex is " + sex);
    }
}
@bean
public servletregistrationbean registerservlet() {
    servletregistrationbean servletregistrationbean = new servletregistrationbean(new registerservlet(), "/registerservlet");
    servletregistrationbean.addinitparameter("name", "javastack");
    servletregistrationbean.addinitparameter("sex", "man");
    return servletregistrationbean;
}

二、servlet 3.0 之前，servlet、filter、listener 这些组件都需要在 web.xml 中进行配置，3.0 之后开始不再需要 web.xml 这个配置文件了，所有的组件都可以通过代码配置或者注解@webservlet/@webfilter/@weblistener来达到目的。

import javax.servlet.annotation.webinitparam;
import javax.servlet.annotation.webservlet;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import java.io.ioexception;
@webservlet(name = "javaservlet", urlpatterns = "/javastack.cn", asyncsupported = true,
        initparams = {
        @webinitparam(name = "name", value = "javastack"),
        @webinitparam(name = "sex", value = "man") })
public class javaservlet extends httpservlet {
    @override
    protected void service(httpservletrequest req, httpservletresponse resp) throws ioexception {
        string name = getservletconfig().getinitparameter("name");
        string sex = getservletconfig().getinitparameter("sex");
        resp.getoutputstream().println("name is " + name);
        resp.getoutputstream().println("sex is " + sex);
    }
}

注意：需要在启动类上配置上注解@servletcomponentscan来扫描这三个注解@servletcomponentscan扫描@webservlet和@webfilter及@weblistener的配置

三、实现org.springframework.boot.web.servlet.servletcontextinitializer向容器中注入bean的方式动态注册

import javax.servlet.annotation.webinitparam;
import javax.servlet.annotation.webservlet;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import java.io.ioexception;
@webservlet(name = "javaservlet", urlpatterns = "/javastack.cn", asyncsupported = true,
        initparams = {
        @webinitparam(name = "name", value = "javastack"),
        @webinitparam(name = "sex", value = "man") })
public class javaservlet extends httpservlet {
    @override
    protected void service(httpservletrequest req, httpservletresponse resp) throws ioexception {
        string name = getservletconfig().getinitparameter("name");
        string sex = getservletconfig().getinitparameter("sex");
        resp.getoutputstream().println("name is " + name);
        resp.getoutputstream().println("sex is " + sex);
    }
}
import cn.javastack.springbootbestpractice.servlet.initservlet;
import org.springframework.boot.web.servlet.servletcontextinitializer;
import org.springframework.stereotype.component;
import javax.servlet.servletcontext;
import javax.servlet.servletregistration;
@component
public class servletconfig implements servletcontextinitializer {
    @override
    public void onstartup(servletcontext servletcontext) {
        servletregistration initservlet = servletcontext.addservlet("initservlet", initservlet.class);
        initservlet.addmapping("/initservlet");
        initservlet.setinitparameter("name", "javastack");
        initservlet.setinitparameter("sex", "man");
    }
}

四、使用org.springframework.web.servlet.mvc.method.annotation.requestmappinghandlermapping.registermapping()方法运行时动态注册

   private void registerserverendpoint(string path, object bean) throws nosuchmethodexception {
        requestmappinghandlermapping mapping = applicationcontext.getbean(requestmappinghandlermapping.class);
        requestmappinginfo.builderconfiguration config = new requestmappinginfo.builderconfiguration();
        if (webmvcproperties.getpathmatch().getmatchingstrategy() == webmvcproperties.matchingstrategy.path_pattern_parser) {
            config.setpatternparser(new pathpatternparser());
        } else {
            config.setpathmatcher(new antpathmatcher());
        }
        requestmappinginfo handleget = requestmappinginfo.paths(path).methods(requestmethod.get).options(config).build();
        mapping.registermapping(handleget, bean, servlethttphandler.class.getmethod("handleget"));
        requestmappinginfo handlepost = requestmappinginfo.paths(path).methods(requestmethod.post).options(config).build();
        mapping.registermapping(handlepost, bean, servlethttphandler.class.getmethod("handlepost", string.class));
    }

五、使用org.springframework.web.servlet.function.routerfunction注册

import com.fasterxml.jackson.databind.objectmapper;
import lombok.extern.slf4j.slf4j;
import org.springframework.http.mediatype;
import org.springframework.web.servlet.function.routerfunction;
import org.springframework.web.servlet.function.routerfunctions;
import org.springframework.web.servlet.function.serverrequest;
import org.springframework.web.servlet.function.serverresponse;
import javax.servlet.servletexception;
import java.io.ioexception;
import java.time.duration;
import java.util.hashmap;
import java.util.list;
import java.util.map;
import java.util.uuid;
public class streamserver {
    private final objectmapper objectmapper = new objectmapper();
    private final string endpoint;
    private final routerfunction<serverresponse> router;
    public streamserver(string endpoint) {
        this.endpoint = endpoint;
        this.router = routerfunctions.route()
                .post(this.endpoint, this::handlepost)
                .build();
    }
    public routerfunction<serverresponse> getrouter() {
        return this.router;
    }
    private serverresponse handlepost(serverrequest request) throws servletexception, ioexception {
        list<mediatype> acceptheaders = request.headers().ashttpheaders().getaccept();
        if (!acceptheaders.contains(mediatype.text_event_stream)
                || !acceptheaders.contains(mediatype.application_json)) {
            return serverresponse.badrequest()
                    .body("invalid accept headers. expected text_event_stream and application_json");
        }
        string body = request.body(string.class);
        log.info("body:{}", body);
        string sessionid = uuid.randomuuid().tostring();
        return serverresponse.sse(ssebuilder -> {
            ssebuilder.oncomplete(() -> {
                log.debug("request response stream completed for session: {}", sessionid);
            });
            ssebuilder.ontimeout(() -> {
                log.debug("request response stream timed out for session: {}", sessionid);
            });
            try {
                for (int i = 0; i < 100; ++i) {
                    map<string, object> row = new hashmap<>();
                    row.put("rowid", i + 1);
                    row.put("rowname", i + 1);
                    string json = objectmapper.writevalueasstring(row);
                    ssebuilder.id(sessionid)
                            .event("message")
                            .data(json);
                }
                ssebuilder.complete();
            } catch (exception e) {
                log.error("failed to handle request stream: {}", e.getmessage());
                ssebuilder.error(e);
            }
        }, duration.zero);
    }
}
import com.github.kylewka.smartai.demo.stream.streamserver;
import org.springframework.context.annotation.bean;
import org.springframework.context.annotation.configuration;
import org.springframework.web.servlet.function.routerfunction;
import org.springframework.web.servlet.function.serverresponse;
@configuration
public class streamserverconfig {
    @bean
    public streamserver streamserver() {
        return new streamserver("/test/stream");
    }
    @bean
    public routerfunction<serverresponse> sseroute(streamserver streamserver) {
        return streamserver.getrouter();
    }
}