1.WkTests  简单测试生成图片

import java.io.IOException;

public class WkTests {
    public static void main(String[] args) {
        String cmd="F:/wkhtmltopdf/bin/wkhtmltoimage --quality 75 https://www.nowcoder.com d:/work/data/wk-images/3.png";

        try {
            Runtime.getRuntime().exec(cmd);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

2.配置 生成图片的命令 和 图片储存路径

#wk
wk:
  image:
    command: F:/wkhtmltopdf/bin/wkhtmltoimage
    storage: d:/work/data/wk-images

3.在程序启动时，自动创建图片储存路径  WkConfig

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;

import javax.annotation.PostConstruct;
import java.io.File;

@Configuration
public class WkConfig {

    private static Logger logger= LoggerFactory.getLogger(WkConfig.class);

    @Value("${wk.image.storage}")
    private String wkImageStorage;

    @PostConstruct
    public void init(){
        //创建wk图片目录
        File file = new File(wkImageStorage);
        if (!file.exists()){
            file.mkdir();
            logger.info("创建wk图片目录："+wkImageStorage);
        }
    }
}

4.ShareController

import com.nowcoder.community.entity.Event;
import com.nowcoder.community.event.EventProducer;
import com.nowcoder.community.util.CommunityConstant;
import com.nowcoder.community.util.CommunityUtil;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.ResponseBody;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

@Controller
public class ShareController implements CommunityConstant {

    private static final Logger logger= LoggerFactory.getLogger(ShareController.class);

    @Autowired
    private EventProducer eventProducer;

    @Value("${community.path.domain}")
    private String domain;

    @Value("${server.servlet.context-path}")
    private String contextPath;

    @Value("${wk.image.storage}")
    private String wkImageStorage;

    @GetMapping("/share")
    @ResponseBody
    public String share(String htmlUrl){
        //文件名
        String fileName = CommunityUtil.generateUUID();

        //异步生成长图
        Event event = new Event()
                .setTopic(TOPIC_SHARE)
                .setData("htmlUrl",htmlUrl)
                .setData("fileName",fileName)
                .setData("suffix",".png");
        eventProducer.fireEvent(event);

        //返回访问路径
        Map<String,Object> map=new HashMap<>();
        map.put("shareUrl",domain+contextPath+"/share/image/"+fileName);

        return CommunityUtil.getJSONString(0,null,map);
    }

    //获取长图
    @GetMapping("/share/image/{fileName}")
    public void getShareImage(@PathVariable("fileName") String fileName, HttpServletResponse response){
        if (StringUtils.isBlank(fileName)){
            throw new IllegalArgumentException("文件名不能为空!");
        }

        response.setContentType("image/png");
        File file=new File(wkImageStorage+"/"+fileName+".png");

        try {
            ServletOutputStream os = response.getOutputStream();
            FileInputStream fis=new FileInputStream(file);
            byte[] buffer=new byte[1024];
            int len=0;
            while ((len= fis.read(buffer))!=-1){
                os.write(buffer,0,len);
            }
        } catch (IOException e) {
            logger.error("获取长图失败："+e.getMessage());
        }
    }
}

5.创建消费分享事件 EventConsumer

import com.alibaba.fastjson.JSONObject;
import com.nowcoder.community.entity.DiscussPost;
import com.nowcoder.community.entity.Event;
import com.nowcoder.community.entity.Message;
import com.nowcoder.community.service.DiscussPostServiceImpl;
import com.nowcoder.community.service.ElasticsearchService;
import com.nowcoder.community.service.MessageServiceImpl;
import com.nowcoder.community.util.CommunityConstant;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.kafka.annotation.KafkaListener;
import org.springframework.stereotype.Component;

import java.io.IOException;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

@Component
public class EventConsumer implements CommunityConstant {

    private static final Logger logger= LoggerFactory.getLogger(EventConsumer.class);

    @Autowired
    private MessageServiceImpl messageService;

    @Autowired
    private DiscussPostServiceImpl discussPostService;

    @Autowired
    private ElasticsearchService elasticsearchService;

    @Value("${wk.image.command}")
    private String wkImageCommand;

    @Value("${wk.image.storage}")
    private String wkImageStorage;

    @KafkaListener(topics = {TOPIC_COMMENT,TOPIC_FOLLOW,TOPIC_LIKE})
    public void handleCommentMessage(ConsumerRecord record){
        if (record==null||record.value()==null){
            logger.error("消息的内容为空!");
            return;
        }

        Event event= JSONObject.parseObject(record.value().toString(),Event.class);
        if (event==null){
            logger.error("消息格式错误!");
            return;
        }

        //发送站内通知
        Message message=new Message();
        message.setFromId(SYSTEM_USER_ID);
        message.setToId(event.getEntityUserId());
        message.setConversationId(event.getTopic());
        message.setCreateTime(new Date());

        Map<String,Object> content=new HashMap<>();
        content.put("userId",event.getUserId());
        content.put("entityType",event.getEntityType());
        content.put("entityId",event.getEntityId());

        if (!event.getData().isEmpty()){
            for (Map.Entry<String, Object> entry : event.getData().entrySet()) {
                content.put(entry.getKey(), entry.getValue());
            }
        }

        message.setContent(JSONObject.toJSONString(content));
        messageService.addMessage(message);
    }

    //消费发帖事件
    @KafkaListener(topics = {TOPIC_PUBLISH})
    public void handlePublishMessage(ConsumerRecord record){
        if (record==null||record.value()==null){
            logger.error("消息的内容为空!");
            return;
        }

        Event event=JSONObject.parseObject(record.value().toString(),Event.class);
        if (event==null){
            logger.error("消息格式错误!");
            return;
        }

        DiscussPost post = discussPostService.selectDiscussPostById(event.getEntityId());
        elasticsearchService.saveDiscussPost(post);
    }

    //消费删帖事件
    @KafkaListener(topics = {TOPIC_DELETE})
    public void handleDeleteMessage(ConsumerRecord record){
        if (record==null||record.value()==null){
            logger.error("消息的内容为空!");
            return;
        }

        Event event = JSONObject.parseObject(record.value().toString(), Event.class);
        if (event==null){
            logger.error("消息格式错误!");
            return;
        }

        elasticsearchService.deleteDiscussPost(event.getEntityId());
    }

    //消费分享事件
    @KafkaListener(topics = {TOPIC_SHARE})
    public void handleShareMessage(ConsumerRecord record){
        if (record==null||record.value()==null){
            logger.error("消息格式错误!");
            return;
        }

        Event event=JSONObject.parseObject(record.value().toString(),Event.class);
        if (event==null){
            logger.error("消息格式错误!");
            return;
        }

        String htmlUrl = (String) event.getData().get("htmlUrl");
        String fileName = (String) event.getData().get("fileName");
        String suffix = (String) event.getData().get("suffix");

        String cmd=wkImageCommand+" --quality 75 "+htmlUrl+" "+wkImageStorage+"/"+fileName+suffix;

        try {
            Runtime.getRuntime().exec(cmd);
            logger.info("生成长图成功："+cmd);
        } catch (IOException e) {
            logger.error("生成长图失败："+e.getMessage());
        }
    }
}