url2pdf

A simple service that convert target url to pdf via http or https protocol by invoking wkhtmltopdf, it's stateless, horizontal scalable.

Prerequists

wkhtmltopdf

You have to install wkhtmltopdf first, otherwise url2pdf won't startup successful. Follow the instructions from wkhtmltopdf based on your operating system.

java 1.8

This service requires java 1.8.

Running

Execute ./gradlew build at command line interface, then packaged war file will be build/libs, deploy the war file to any java container, i.e. Tomcat, JBoss.

Or just ./gradlew bootRun.

Usages

http://example.com/url2pdf?target=www.google.com.tw

There are two possible usages:

1. proxy: Invoking url above programmatically via http or https protocol, read converted result from service response's body, then send back to clients. [clients] <--> [our services] <--> [url2pdf]
2. direct: Add a link tag in html, make clients invoking url above from their browser directly, see Abuse Prevention. [clients] <--> [url2pdf]

Query Parameters

Name	Enums	Example	Required	Default	wkhtmltopdf option
target		www.google.com.tw	yes
filename		converted.pdf	no	result.pdf
orientation	[LANDSCAPE, PORTRAILT]	PORTRAILT	no	PORTRAILT	--orientation
pageSize	[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, B0, B1, B2, B3, B4, B5, B6, B7, B8, B9, B10, LETTER]	B3	no	A4	--page-size
viewport		1280x1024	no	800x600	--viewport-size

If you want to develop more wkhtmltopdf options, see wkhtmltopdf.txt for more details.

Restrict IP

url2pdf is not for public purpose but as a organization microservice, so please specify at least one ip prefix of your organization in accept.target.ips.txt.

url2pdf will reject any requests by default if it can't find any specify ip prefixes.

Abuse Prevention & Privacy

It's fine if you let your users convert a public page by their browser directly, but it may cause abuse issues from malicious users. Or you want your users convert a private page which needs some authentications before access. One possible solution is Hash-based_message_authentication_code.

Simply says, your service should sign the requested url, give it to your users, then your verify the signed request from url2pdf to make sure it is permitted by your service.

For example, you want your users get a pdf file by converting http://target-service.com/private-page.html, so we will have

http://example.com/url2pdf?target=http://target-service.com/private-page.html&viewport=1280x1024&timestamp=1452609375

target-service.com should sign this url by hmac function from its private key, append calculated hash:

2a1d7c2f78783913492e86730a4aaf1c9a71033e = hmac(target, viewport, timestamp, private key)

http://example.com/url2pdf?target=http://target-service.com/private-page.html&viewport=1280x1024&timestamp=1452609375&hash=2a1d7c2f78783913492e86730a4aaf1c9a71033e
                                                                                                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Then target-service.com should verify request from url2pdf by calculating hash value using hmac function above, check calculated hash value is match the hash value append from request.

Of course, in this scenario private-page.html should allow any ip to access or protected by firewall, vpn...etc.

Fonts

It might render incorrectly or blank due to lack of fonts required by html(i.e. Chinese, Japanese or special sympols). Add required fonts to OS or using css web fonts are two possible solutions.

Docker

1. Build jar: ./gradlew jar
2. Build docker image: sudo docker build -t url2pdf .
3. Run docker container: sudo docker run -d -p 8080:8080 --name url2pdf url2pdf
4. (optional) DeleteRUN apt-get install -y ttf-wqy-microhei if you don't need tranditional chinese fonts.

Acknowledge

This url2pdf idea is inspired by an article Spring From the Trenches: Creating PDF Documents With Wkhtmltopdf.