java - 官方 supercsv 推土机示例不适用于 Play — Play 2.1.1，Java

Question

更新:

现在我发现了一个很奇怪的东西，当我直接把编译好的测试类放上去的时候就可以了 进入结构与 svn 仓库相同的“super-csv-dozer-2.1.0.jar”。 但是，一旦我使用自己的包，它就无法工作。我总是使用整个路径 像这样:myPackage.csv.SurveyResponse.class 我错过了什么？为什么它在普通的 Java 项目中有效，但在 Play 项目中却无效？ 我还在 eclipse 之外的另一个目录中尝试过它，但没有从 可能混淆路径的svn repo。我尝试的另一件事是将 Writing.class 放入不同的包中，但没有帮助。

原问题:

我正在尝试在 Play 项目中将 SuperCSV 与 Dozer 结合使用。 官方 supercsv 示例在单独的 Java 项目中运行良好。 但是，当我将代码和所需的 SuperCSV Jars 放入新创建的 Play 项目中时，我总是 在这行代码中获取 SurveyResponse.class 的 ClassNotfoundException: beanWriter.configureBeanMapping(myPackage.csv.SurveyResponse.class, FIELD_MAPPING);

这是我的项目结构的截图: http://oi44.tinypic.com/mrqp7s.jpg

我确保所有 JARS 都可用，我将它们非托管地放入/lib 文件夹中， 它们在 eclipse 中可用，并且在编译期间不会出现错误。 我调试了代码，找到了 SurveyResponse.class 并初始化了 beanWriter。 所以 Play 必须以某种方式在后台做一些魔术来触发这个错误。 游戏在后台做什么可能会触发这种奇怪的行为？ 我可以尝试做些什么来解决这个问题？

我对示例所做的更改使其适用于 Play: 我使用了与官方 supercsv 示例完全相同的代码。 我所做的唯一更改是删除 Writing.main(..) 方法并设置方法 Writing.writeWithDozerCsvBeanWriter() 并将 Writing.partialWriteWithCsvDozerBeanWriter() 公开，因此可以从应用程序 Controller 访问它。 当然，我将所有类中的包名称更改为 package myPackage.test；

示例链接: 在评论中看到，由于声誉低，我不能添加超过 2 个链接。

Controller :

public class Application extends Controller {
    public static Result index() throws Exception  {
        Writing.writeWithDozerCsvBeanWriter();
        Writing.partialWriteWithCsvDozerBeanWriter();
        return ok(index.render("Your new application is ready."));
    } 
}

Writing类触发错误的代码:

ICsvDozerBeanWriter beanWriter = null;
    try {
        beanWriter = new CsvDozerBeanWriter(new FileWriter("target/writeWithCsvDozerBeanWriter.csv"),
            CsvPreference.STANDARD_PREFERENCE);
        
        // configure the mapping from the fields to the CSV columns
        //Here the exception occures:
        beanWriter.configureBeanMapping(myPackage.csv.SurveyResponse.class, FIELD_MAPPING);

堆栈跟踪:

play.api.Application$$anon$1: Execution exception[[MappingException: java.lang.ClassNotFoundException: myPackage.test.SurveyResponse]]
    at play.api.Application$class.handleError(Application.scala:289) ~[play_2.10.jar:2.1.1]
    at play.api.DefaultApplication.handleError(Application.scala:383) [play_2.10.jar:2.1.1]
    at play.core.server.netty.PlayDefaultUpstreamHandler$$anon$2$$anonfun$handle$1.apply(PlayDefaultUpstreamHandler.scala:144) [play_2.10.jar:2.1.1]
    at play.core.server.netty.PlayDefaultUpstreamHandler$$anon$2$$anonfun$handle$1.apply(PlayDefaultUpstreamHandler.scala:140) [play_2.10.jar:2.1.1]
    at play.api.libs.concurrent.PlayPromise$$anonfun$extend1$1.apply(Promise.scala:113) [play_2.10.jar:2.1.1]
    at play.api.libs.concurrent.PlayPromise$$anonfun$extend1$1.apply(Promise.scala:113) [play_2.10.jar:2.1.1]
    at play.api.libs.concurrent.PlayPromise$$anonfun$extend$1$$anonfun$apply$1.apply(Promise.scala:104) [play_2.10.jar:2.1.1]
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24) [scala-library.jar:na]
    at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24) [scala-library.jar:na]
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source) [na:1.6.0_37]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [na:1.6.0_37]
    at java.lang.Thread.run(Unknown Source) [na:1.6.0_37]
org.dozer.MappingException: java.lang.ClassNotFoundException: myPackage.test.SurveyResponse
    at org.dozer.util.MappingUtils.throwMappingException(MappingUtils.java:82) ~[dozer-5.4.0.jar:na]
    at org.dozer.util.DefaultClassLoader.loadClass(DefaultClassLoader.java:38) ~[dozer-5.4.0.jar:na]
    at org.dozer.util.MappingUtils.loadClass(MappingUtils.java:224) ~[dozer-5.4.0.jar:na]
    at org.dozer.loader.DozerBuilder$MappingBuilder.classA(DozerBuilder.java:129) ~[dozer-5.4.0.jar:na]
    at org.dozer.loader.api.BeanMappingBuilder.mapping(BeanMappingBuilder.java:72) ~[dozer-5.4.0.jar:na]
    at org.dozer.loader.api.BeanMappingBuilder.mapping(BeanMappingBuilder.java:67) ~[dozer-5.4.0.jar:na]
    at org.supercsv.io.dozer.CsvDozerBeanWriter$MappingBuilder.configure(CsvDozerBeanWriter.java:178) ~[super-csv-dozer-2.1.0.jar:na]
    at org.dozer.loader.api.BeanMappingBuilder.build(BeanMappingBuilder.java:42) ~[dozer-5.4.0.jar:na]
    at org.dozer.DozerBeanMapper.addMapping(DozerBeanMapper.java:258) ~[dozer-5.4.0.jar:na]
    at org.supercsv.io.dozer.CsvDozerBeanWriter.configureBeanMapping(CsvDozerBeanWriter.java:91) ~[super-csv-dozer-2.1.0.jar:na]
    at myPackage.test.Writing.writeWithDozerCsvBeanWriter(Writing.java:88) ~[na:na]
    at controllers.Application.index(Application.java:12) ~[na:na]
    at Routes$$anonfun$routes$1$$anonfun$applyOrElse$1$$anonfun$apply$1.apply(routes_routing.scala:49) ~[na:na]
    at Routes$$anonfun$routes$1$$anonfun$applyOrElse$1$$anonfun$apply$1.apply(routes_routing.scala:49) ~[na:na]
    at play.core.Router$HandlerInvoker$$anon$6$$anon$2.invocation(Router.scala:164) ~[play_2.10.jar:2.1.1]
    at play.core.Router$Routes$$anon$1.invocation(Router.scala:345) ~[play_2.10.jar:2.1.1]
    at play.core.j.JavaAction$$anon$1.call(JavaAction.scala:31) ~[play_2.10.jar:2.1.1]
    at play.core.j.JavaAction$$anon$2.apply(JavaAction.scala:74) ~[play_2.10.jar:2.1.1]
    at play.core.j.JavaAction$$anon$2.apply(JavaAction.scala:73) ~[play_2.10.jar:2.1.1]
    at play.libs.F$Promise$PromiseActor.onReceive(F.java:420) ~[play_2.10.jar:2.1.1]
    at akka.actor.UntypedActor$$anonfun$receive$1.applyOrElse(UntypedActor.scala:159) ~[akka-actor_2.10.jar:na]
    at akka.actor.ActorCell.receiveMessage(ActorCell.scala:425) ~[akka-actor_2.10.jar:na]
    at akka.actor.ActorCell.invoke(ActorCell.scala:386) ~[akka-actor_2.10.jar:na]
    at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:230) ~[akka-actor_2.10.jar:na]
    at akka.dispatch.Mailbox.run(Mailbox.scala:212) ~[akka-actor_2.10.jar:na]
    at akka.dispatch.ForkJoinExecutorConfigurator$MailboxExecutionTask.exec(AbstractDispatcher.scala:502) ~[akka-actor_2.10.jar:na]
    at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:262) ~[scala-library.jar:na]
    at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:975) ~[scala-library.jar:na]
    at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1478) ~[scala-library.jar:na]
    at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:104) ~[scala-library.jar:na]
Caused by: java.lang.ClassNotFoundException: myPackage.test.SurveyResponse
    at java.net.URLClassLoader$1.run(Unknown Source) ~[na:1.6.0_37]
    at java.security.AccessController.doPrivileged(Native Method) ~[na:1.6.0_37]
    at java.net.URLClassLoader.findClass(Unknown Source) ~[na:1.6.0_37]
    at java.lang.ClassLoader.loadClass(Unknown Source) ~[na:1.6.0_37]
    at java.lang.ClassLoader.loadClass(Unknown Source) ~[na:1.6.0_37]
    at sbt.PlayCommands$$anonfun$53$$anonfun$55$$anon$2.loadClass(PlayCommands.scala:535) ~[na:na]
    at java.lang.Class.forName0(Native Method) ~[na:1.6.0_37]
    at java.lang.Class.forName(Unknown Source) ~[na:1.6.0_37]
    at org.apache.commons.lang3.ClassUtils.getClass(ClassUtils.java:823) ~[commons-lang3.jar:3.1]
    at org.apache.commons.lang3.ClassUtils.getClass(ClassUtils.java:889) ~[commons-lang3.jar:3.1]
    at org.apache.commons.lang3.ClassUtils.getClass(ClassUtils.java:872) ~[commons-lang3.jar:3.1]
    at org.dozer.util.DefaultClassLoader.loadClass(DefaultClassLoader.java:36) ~[dozer-5.4.0.jar:na]
    ... 28 common frames omitted

额外信息: 我仍然无法解决问题，但这里有一些额外的信息可以缩小问题的范围: 当我删除 configureBeanMapping 方法调用时，csv header 已成功写入文件(请参见下面的代码)。 当我对填充的 SurveyResponse 对象执行 System.out.println() 时，SurveyResponse 类也在工作(请参见下面的代码)。 所以这不是包名或类名的问题。

只写头部的修改代码:

//...more code
myPackage.csv.SurveyResponse response3 = new myPackage.csv.SurveyResponse(42, false, Arrays.asList(new Answer(1, null), new Answer(2,
    "Carl Sagan"), new Answer(3, "Star Wars")));
final List<myPackage.csv.SurveyResponse> surveyResponses = Arrays.asList(response1, response2, response3);

ICsvDozerBeanWriter beanWriter = null;
try {
    beanWriter = new CsvDozerBeanWriter(new FileWriter("target/writeWithCsvDozerBeanWriter.csv"),
        CsvPreference.STANDARD_PREFERENCE);
    
    // configure the mapping from the fields to the CSV columns
    //beanWriter.configureBeanMapping(myPackage.csv.SurveyResponse.class, FIELD_MAPPING);
    
    //Prints the value 42 successfully
    System.out.println(response3.getAge());
    
    // write the header
    beanWriter.writeHeader("age", "consentGiven", "questionNo1", "answer1", "questionNo2", "answer2","questionNo3", "answer3");

//...more code

Answer 1

据我从错误中了解到，Play 正在尝试加载错误的类。看看这一行:

java.lang.ClassNotFoundException: org.supercsv.mock.dozer.SurveyResponse

我认为 SurverResponse 是您自己的项目类之一，而不是 SuperCSV 的一部分。尝试使用完整路径作为前缀，例如:

beanWriter.configureBeanMapping(whateverpackage.models.SurveyResponse.class, FIELD_MAPPING);