at sun.awt.FontConfiguration.getVersion(FontConfiguration.java:1264)報錯問題解決

參考https://www.dazhuanlan.com/2020/02/02/5e3649c14e598/所述方法，可解決問題。

原因：
項目中需要使用圖形驗證碼，本地使用沒問題，部署到線上出現以下問題：

java.lang.NullPointerException: null
        at sun.awt.FontConfiguration.getVersion(FontConfiguration.java:1264)
        at sun.awt.FontConfiguration.readFontConfigFile(FontConfiguration.java:219)
        at sun.awt.FontConfiguration.init(FontConfiguration.java:107)
        at sun.awt.X11FontManager.createFontConfiguration(X11FontManager.java:774)
        at sun.font.SunFontManager$2.run(SunFontManager.java:431)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.font.SunFontManager.<init>(SunFontManager.java:376)
        at sun.awt.FcFontManager.<init>(FcFontManager.java:35)
        at sun.awt.X11FontManager.<init>(X11FontManager.java:57)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
        at java.lang.Class.newInstance(Class.java:442)
        at sun.font.FontManagerFactory$1.run(FontManagerFactory.java:83)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.font.FontManagerFactory.getInstance(FontManagerFactory.java:74)

主要原因是字體問題，修改方案如下：
只需要在項目的docker部署文件裏面添加下面這一條即可：

RUN apk add --update ttf-dejavu fontconfig

添加後配置文件如下：

FROM openjdk:8-jdk-alpine
VOLUME /tmp
ADD xx.jar app.jar
RUN apk add --update ttf-dejavu fontconfig
ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]