Deprecated. ~User Script for docs.spring.io code highlight~ go to https://gist.github.com/theand/90f75fc03b8a32feff4473c1c97277b9

docs-spring-io-code-syntax.user.js

// ==UserScript==
// @name        docs.spring.io code highlight
// @namespace   http://127.0.0.1
// @description User Script for docs.spring.io code highlight
// @author      Heesang Chae
// @include     http://docs.spring.io/*
// @require     https://cdn.jsdelivr.net/prism/1.6.0/prism.js
// @require     https://cdn.jsdelivr.net/prism/1.6.0/components/prism-java.min.js
// @require     https://cdn.jsdelivr.net/gh/mathiasbynens/he@v1.1.1/he.js
// @version     2017.07.18
// @grant       none

// ==/UserScript==

var userscript = function (Prism, he) {

    console.log("init : docs.spring.io Code Syntax - " + document.location.toString());

    try {

        document.querySelectorAll("pre.code").forEach(e => {
            const text = he.decode(e.innerHTML);
            const html = Prism.highlight(text, Prism.languages.java);

            const newCode = document.createElement('code');
            newCode.setAttribute('class', 'language-java');
            newCode.innerHTML = html;

            const newPre = document.createElement('pre');
            newPre.appendChild(newCode);

            e.parentNode.replaceChild(newPre, e);
        });

    } catch (err) {
        console.error("UserScript : " + err.toString());
    }
};

window.prismjs = Prism;
window.hejs = he;

setTimeout(() => {

    var el = document.createElement('script');
    el.type = 'text/javascript';
    el.text = '(' + userscript + ')(window.prismjs, window.hejs);';
    document.head.appendChild(el);


}, 500);

function injectStyleSheet(href) {
    var link  = document.createElement('link');
    link.rel  = 'stylesheet';
    link.href = href;
    document.head.appendChild(link);
}

injectStyleSheet("https://cdn.jsdelivr.net/prism/1.6.0/themes/prism.css");

left - userscript applied.
right - original