如何让jjs –add-opens在java9中工作？

2019年7月28日 386次阅读

我一直在使用
https://apimeister.com/2015/06/27/add-jar-to-the-classpath-at-runtime-in-jjs.html的反射技术在运行时在java的nashorn jjs中加载类.

它适用于java 8,但在java 9中却没有.我知道https://stackoverflow.com/a/41265267/5891192中提到的推荐命令行解决方法

并且根据https://stackoverflow.com/a/45970885/5891192,使用=而不是标志和它的args之间的空格的替代语法似乎它也应该是有效的(需要因为nashorn方法通过-J – …传递jjm args到jjs.

任何提示？

这工作……(java 8)…

$wget -q http://central.maven.org/maven2/org/apache/poi/poi/4.0.0/poi-4.0.0.jar
$/usr/lib/jvm/java-1.8.0/bin/jjs -scripting loadit.js -- poi-4.0.0.jar
DONE

这不…(java 9)…

$wget -q http://central.maven.org/maven2/org/apache/poi/poi/4.0.0/poi-4.0.0.jar
$/usr/lib/jvm/java-9/bin/jjs -J--add-opens=java.base/java.net=ALL-UNNAMED -scripting loadit.js -- poi-4.0.0.jar

Exception in thread "main" java.lang.reflect.InaccessibleObjectException: Unable to make protected void java.net.URLClassLoader.addURL(java.net.URL) accessible: module java.base does not "opens java.net" to module jdk.scripting.nashorn.scripts
at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(AccessibleObject.java:337)...

这是loadit.js ……

// loadit.js 
function addUrlToClasspath(pth) {
  var s = java.lang.ClassLoader.getSystemClassLoader();
  var C = Java.type("java.lang.Class[]");
  var p = new C(1); p[0]  = java.net.URL.class;
  var m = java.net.URLClassLoader.class.getDeclaredMethod("addURL", p);
  var O = Java.type("java.lang.Object[]"); var a = new O(1); var f = new java.io.File(pth); m.setAccessible(true);
  var u = f.toURL(); a[0] = u; m.invoke(s, a);
}

addUrlToClasspath($ARG[0]);
print("DONE")

编辑：2018年10月23日：更正了“This does not(java 9)”示例命令行

最佳答案 正如我上面评论的,实际上有3个问题.

>问题问题 – 答案：a.没有帮助(见下一点)b.系统级别add-opens命令行选项不会进入jjs使用的Nashorn引擎
>无论如何,从java9到Java 9, compatability issue with ClassLoader.getSystemClassLoader开始,附加到系统类的加载器方法都不起作用
>从java-11开始,jjs本身被声明为不推荐使用

但是,多亏了@Alan,@Holger和我的同事@Philippe的提示,我得到了我想要的解决方法.

>您可以使用所需的jar创建自己的URLClassLoader,并创建传入此类加载器的第二个nashorn引擎(例如来自jjs的命令行参数).
>添加另一个hack,用于为脚本中的脚本实现所谓的“here document”

……这是一个完整的例子：

// jjs -scripting ora2csv.js -- "select 'hi' from dual" jdbc:oracle:thin:@host:1521:XE user pass

function newJjsEngineWith (jars) {
  var ua = Java.type("java.net.URL[]"); var urls = new ua(jars.length);
  for(var i=0; i<jars.length; i++) {
    var u=new java.net.URL(new java.io.File(jars[i]).toURL());
    urls[i] = u;
  }
  var loader = new java.net.URLClassLoader(urls);
  java.lang.Thread.currentThread().setContextClassLoader(loader);
  var nsef = Java.type("jdk.nashorn.api.scripting.NashornScriptEngineFactory");
  var sa = Java.type("java.lang.String[]"); var args = new sa(2 + $ARG.length);
  args[0] = "-scripting"; args[1] = "--";
  for(var i=0;i<$ARG.length;i++) { args[i+2] = $ARG[i]; }
  return new nsef().getScriptEngine(args, loader);
}

var jjs = newJjsEngineWith(["ojdbc8.jar"]);

function hereDoc(f) { return f.toString().slice(14,-3); }

var code = hereDoc(function(){/*
var q = $ARG[0]; // select 'hello' from dual
var c = $ARG[1]; // jdbc:oracle:thin:@host:1521:XW
var u = $ARG[2]; // username
var p = $ARG[3]; // password
var conn = java.sql.DriverManager.getConnection(c, u, p);
var stmt = conn.createStatement(); rset = stmt.executeQuery(q);
var row=0;
while (rset.next()) {
  row++; var rowBuf = new java.lang.StringBuilder();
  var meta = rset.getMetaData();
  for(var col=0; col< meta.getColumnCount(); col++) {
    var cell = rset.getString(col+1);
    if (cell == null) { cell = ""; }
    rowBuf.append(cell.replaceAll(";",","));
    if (col < meta.getColumnCount()-1) { rowBuf.append(";"); }
  }
  print(rowBuf.toString());
}
stmt.close();
*/});

jjs.eval(code);

这适用于java 8到java 11.

$/usr/lib/jvm/java-1.8.0/bin/jjs -scripting ora2csv.js -- "select 'hi' from dual" jdbc:oracle:thin:@host:1521:XE user pass
hi
$/usr/lib/jvm/java-9/bin/jjs -scripting ora2csv.js -- "select 'hi' from dual" jdbc:oracle:thin:@host:1521:XE user pass
hi
$/usr/lib/jvm/java-10/bin/jjs -scripting ora2csv.js -- "select 'hi' from dual" jdbc:oracle:thin:@host:1521:XE user pass
hi
$/usr/lib/jvm/java-11/bin/jjs -scripting ora2csv.js -- "select 'hi' from dual" jdbc:oracle:thin:@host:1521:XE user pass
Warning: The jjs tool is planned to be removed from a future JDK release
Warning: Nashorn engine is planned to be removed from a future JDK release
hi

我欢迎任何建议,使这更简洁,更少pukey

点赞