需求

用户可以选择以长图的形式分享本网页

方法

• wkhtmltopdf
  • wkhtmltopdf url file
  • wkhtmltoimage url file
• java
  • Runtime.getRuntime().exec()

下载

直接去官网下载对应的版本：官网

命令行使用WK

>  wkhtmltopdf https://www.nowcoder.com /opt/project/java/mycommunity-pdfs/1.pdf            
Loading pages (1/6)
Counting pages (2/6)
Resolving links (4/6)
Loading headers and footers (5/6)
Printing pages (6/6)
Done>  wkhtmltoimage  https://www.nowcoder.com /opt/project/java/mycommunity-images/1.png     
Loading page (1/2)
Rendering (2/2)
Done// 上面那条命令生成的长图太大了，可以使用下面这条：以75%的质量输出
>  wkhtmltoimage --quality 75  https://www.nowcoder.com /opt/project/java/mycommunity-images/1.png     
Loading page (1/2)
Rendering (2/2)
Done

在java中调用

application.properties：

mycommunity.path.domain=http://localhost:8080
server.servlet.context-path=/myCommunity
# WK
wk.image.command=/usr/local/bin/wkhtmltoimage
wk.image.storage=/opt/project/java/mycommunity-images/

WK配置类，在每次程序开始运行时自动生成存放图像的文件夹

@Configuration
public class WkConfig {private static final Logger logger = LoggerFactory.getLogger(WkConfig.class);@Value("${wk.image.storage}")private String wkImageStorage;@PostConstructpublic void init(){// create the dic about WKimageFile file = new File(wkImageStorage);if(!file.exists()){file.mkdir();logger.info("create the dictionary of WKimage: " + wkImageStorage);}}
}

调用WK的控制层，因为生成长图比较耗时，所以使用异步操作，在用户操作时调用Kafka的生产者生成事件，通知消费者：

@Controller
public class ShareController implements CommunityConstant {private static final Logger logger = LoggerFactory.getLogger(ShareController.class);@Autowiredprivate EventProducer eventProducer;@Value("${mycommunity.path.domain}")private String domain;@Value("${server.servlet.context-path}")private String contextPath;@Value("${wk.image.storage}")private String wkImageStorage;@GetMapping(path = "/share")@ResponseBodypublic String share(String htmlUrl){// generate the file nameString fileName = CommunityUtil.generateUUID();// Asynchronous generation long picEvent event = new Event().setTopic(TOPIC_SHARE).setData("htmlUrl", htmlUrl).setData("fileName", fileName).setData("suffix", ".png");eventProducer.fireEvent(event);Map<String, Object> map = new HashMap<>();map.put("shareUrl", domain + contextPath + "/share/image" + fileName);return CommunityUtil.getJSONString(0, null, map);}//@GetMapping(path = "/share/image/{fileName}")public void getShareImage(@PathVariable("fileName") String fileName, HttpServletResponse response){if(StringUtils.isBlank(fileName)){throw new IllegalStateException("the file name cannot be blank");}response.setContentType("image/png");File file = new File(wkImageStorage + "/" + fileName + ".png");try {OutputStream os = response.getOutputStream();FileInputStream fis = new FileInputStream(file);byte[] data = new byte[1024];int len = 0;while ((len = fis.read(data)) != -1) {os.write(data, 0, len);}} catch (IOException e) {logger.error("querty the long image failed: ", e.getMessage());}}
}

Kafka的消费者，定义如何消费生成长图的事件：

@Component
public class EventConsumer implements CommunityConstant {@Autowiredprivate static final Logger logger = LoggerFactory.getLogger(EventConsumer.class);@Value("${wk.image.storage}")private String wkImageStorage;@Value("${wk.image.command}")private String wkImageCommand;@KafkaListener(topics = {TOPIC_SHARE})public void handleShareMessage(ConsumerRecord record) {if (record == null || record.value() == null) {logger.error("the content of the message is empty");return;}Event event = JSONObject.parseObject(record.value().toString(), Event.class);if (event == null) {logger.error("message format error");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("generate long image successfully: " + cmd);} catch (IOException e) {logger.info("generate long image fail: " + e.getMessage());}}
}

测试