1. 개요

• 자바 9 이상 사용시
• JreMemoryLeakPreventionListener의 urlCacheProtection 옵션 사용시
• JAR URL connections의 캐싱을 disable 하려면 자바 9에서 추가된 API를 사용한다.

2. 관련 코드

    /**
     * Protect against resources being read for JAR files and, as a side-effect,
     * the JAR file becoming locked. Note this disables caching for all
     * {@link URLConnection}s, regardless of type. Defaults to
     * true.
     */
    private boolean urlCacheProtection = true;
    public boolean isUrlCacheProtection() { return urlCacheProtection; }
    public void setUrlCacheProtection(boolean urlCacheProtection) {
        this.urlCacheProtection = urlCacheProtection;
    }

                /*
                 * Several components end up opening JarURLConnections without
                 * first disabling caching. This effectively locks the file.
                 * Whilst more noticeable and harder to ignore on Windows, it
                 * affects all operating systems.
                 *
                 * Those libraries/components known to trigger this issue
                 * include:
                 * - log4j versions 1.2.15 and earlier
                 * - javax.xml.bind.JAXBContext.newInstance()
                 *
                 * https://bugs.openjdk.java.net/browse/JDK-8163449
                 *
                 * Java 9 onwards disables caching for JAR URLConnections
                 * Java 8 and earlier disables caching for all URLConnections
                 */

                // Set the default URL caching policy to not to cache
                if (urlCacheProtection) {
                    try {
                        JreCompat.getInstance().disableCachingForJarUrlConnections();
                    } catch (IOException e) {
                        log.error(sm.getString("jreLeakListener.jarUrlConnCacheFail"), e);
                    }
                }