import - 字符串模板 : how to import from a jar?

Question

我有一个例子，我从 jar 中包含的文件加载字符串模板组。 使用以下机制可以正常工作:

final String urlName = new StringBuilder()
            .append("jar:file:").append(templateJar.getAbsolutePath()).append("!")
            .append(templateFileName).toString();
final URL url;
try {
        url = new URL(urlName);
} catch (MalformedURLException ex) {
        throw new GeneratorException("bad manifest url", ex);
}
final STGroup stg = new STGroupFile(url, "US-ASCII", '<', '>');

当模板文件包含

时就会出现困难

...
import "../../dataTypeMaps.stg"
...

字符串模板失败并显示以下内容:

can't load group file jar:file:/home/phreed/.m2/repository/edu/vanderbilt/isis/druid/druid-template/2.0.0/druid-template-2.0.0.jar!/template/src/main/java/sponsor/orm/ContractCreator.stg
Caused by: java.lang.IllegalArgumentException: No such group file: ../../dataTypeMaps.stg
    at org.stringtemplate.v4.STGroupFile.<init>(STGroupFile.java:69)
    at org.stringtemplate.v4.STGroup.importTemplates(STGroup.java:570)
    at org.stringtemplate.v4.compiler.GroupParser.group(GroupParser.java:199)
    at org.stringtemplate.v4.STGroup.loadGroupFile(STGroup.java:619)
    at org.stringtemplate.v4.STGroupFile.load(STGroupFile.java:139)
    at org.stringtemplate.v4.STGroupFile.load(STGroupFile.java:128)
    at org.stringtemplate.v4.STGroup.lookupTemplate(STGroup.java:237)
    at org.stringtemplate.v4.STGroup.getInstanceOf(STGroup.java:172)
    at edu.vanderbilt.isis.druid.generator.Generator.build(Generator.java:215)
    at edu.vanderbilt.isis.druid.generator.DruidMojo.execute(DruidMojo.java:193)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:209)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)
    at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:320)
    at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:156)
    at org.apache.maven.cli.MavenCli.execute(MavenCli.java:537)
    at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:196)
    at org.apache.maven.cli.MavenCli.main(MavenCli.java:141)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:290)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:230)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:409)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:352)

是否可以使用 jar 进行设置以便导入能够正常工作？ 当不涉及 jar 时，上述方法可以正常工作。

Answer 1

简单的答案是导入文件的路径错误

...
import "dataTypeMaps.stg"
...

导入将导致从 jar 的根目录开始查找文件。 上述导入相当于将文件放置在...

final String urlName = new StringBuilder()
        .append("jar:file:").append(templateJar.getAbsolutePath()).append("!")
        .append("dataTypeMaps.stg").toString();

我不知道为什么行为与模板组文件位于 native 文件系统上时不同。 为了使其正常工作，我更改了类路径以包含 jar 文件。 由于这是在 Maven 插件上下文中完成的，因此插件需要动态更改类路径。这是通过以下代码完成的...

 public void setTemplateJarName(String templateJarName) throws GeneratorException {
    this.templateJarName = templateJarName;
    final Thread ct = Thread.currentThread();
    final ClassLoader pcl = ct.getContextClassLoader();
    URL[] nurl;
    try {
        nurl = new URL[]{ new URL("file://"+templateJarName) };
    } catch (MalformedURLException ex) {
        throw new GeneratorException("could not load template jar", ex);
    }
    final URLClassLoader ucl = new URLClassLoader(nurl, pcl);
    ct.setContextClassLoader(ucl);
}