java - Play Framework 从字节数组下载图像

Question

我有一些用户上传的图像，我将它们作为字节[]存储在heroku Postgres 数据库上。我正在尝试通过类似于下面的内容的 http 响应下载 jpeg 图像。

ImageModel image = ImageModel.getImage(imageID);
response().setContentType("image/jpeg");
response().setHeader("Content-disposition","attachment; filename=image.jpeg");
return ok(image.imageByteArray);

当我尝试返回它时，出现空指针异常。我正在使用 Ebean 保存和加载我的 ImageModel。当我将模型放入 JsonNode 并返回时，我可以看到该 byte[] 的数据。

"id":1,"imageByteArray":"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123M0B++ILltC8aVM9KZdhxKqNpVN/MXjaeWvS/ILXyJHSy0Xe7s9pcUo0a/lxcdj7Uwxx6tuXPKXF8PD6PZfz6b+R4/fW3mGTxGiTWn5gLUHzLxAIqg73KS0umNpllaVw1oVy9+SDcA5IY0l58SwpSyJ/gI/s0x1sqUlnBKSkpKR/Y/hm/X2L89bhA1NtIfEOh0fycy5rDABgMBGKNv2D+J331g2Crew/wCMsdBq8J5lnBFs9g7csAAeHpv1fA7M36+wfnpUelvMWXI1+fRt8n2z6Fi381JeJdNmukQjkTRNoTYd8QtY7eeBwEzvL63Lly5fS4vn4Zv0/9k=","processedImage":null}

但是，如果我尝试直接从模型引用 byte[]，则会出现空指针异常。我是个 Play 菜鸟，所以我不确定发生了什么。任何帮助将不胜感激。

[error] - application - Exception
java.lang.NullPointerException: null
at java.io.ByteArrayInputStream.<init>(ByteArrayInputStream.java:106) ~[na:1.8.0_51]
at controllers.Application.requestImageFile(Application.java:95) ~[classes/:2.4.2]
at router.Routes$$anonfun$routes$1$$anonfun$applyOrElse$4$$anonfun$apply$4.apply(Routes.scala:208) [classes/:na]
at router.Routes$$anonfun$routes$1$$anonfun$applyOrElse$4$$anonfun$apply$4.apply(Routes.scala:208) [classes/:na]
at play.core.routing.HandlerInvokerFactory$$anon$4.resultCall(HandlerInvoker.scala:136) [play_2.11-2.4.2.jar:2.4.2]
at play.core.routing.HandlerInvokerFactory$JavaActionInvokerFactory$$anon$14$$anon$3$$anon$1.invocation(HandlerInvoker.scala:127) [play_2.11-2.4.2.jar:2.4.2]
at play.core.j.JavaAction$$anon$1.call(JavaAction.scala:70) [play_2.11-2.4.2.jar:2.4.2]
at play.http.DefaultHttpRequestHandler$1.call(DefaultHttpRequestHandler.java:20) [play_2.11-2.4.2.jar:2.4.2]
at play.core.j.JavaAction$$anonfun$7.apply(JavaAction.scala:94) [play_2.11-2.4.2.jar:2.4.2]
at play.core.j.JavaAction$$anonfun$7.apply(JavaAction.scala:94) [play_2.11-2.4.2.jar:2.4.2]
at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24) [scala-library-2.11.6.jar:na]
at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24) [scala-library-2.11.6.jar:na]
at play.core.j.HttpExecutionContext$$anon$2.run(HttpExecutionContext.scala:40) [play_2.11-2.4.2.jar:2.4.2]
at play.api.libs.iteratee.Execution$trampoline$.execute(Execution.scala:70) [play-iteratees_2.11-2.4.2.jar:2.4.2]
at play.core.j.HttpExecutionContext.execute(HttpExecutionContext.scala:32) [play_2.11-2.4.2.jar:2.4.2]
at scala.concurrent.impl.Future$.apply(Future.scala:31) [scala-library-2.11.6.jar:na]
at scala.concurrent.Future$.apply(Future.scala:492) [scala-library-2.11.6.jar:na]
at play.core.j.JavaAction.apply(JavaAction.scala:94) [play_2.11-2.4.2.jar:2.4.2]
at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4$$anonfun$apply$5.apply(Action.scala:105) [play_2.11-2.4.2.jar:2.4.2]
at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4$$anonfun$apply$5.apply(Action.scala:105) [play_2.11-2.4.2.jar:2.4.2]
at play.utils.Threads$.withContextClassLoader(Threads.scala:21) [play_2.11-2.4.2.jar:2.4.2]
at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4.apply(Action.scala:104) [play_2.11-2.4.2.jar:2.4.2]
at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4.apply(Action.scala:103) [play_2.11-2.4.2.jar:2.4.2]
at scala.Option.map(Option.scala:146) [scala-library-2.11.6.jar:na]
at play.api.mvc.Action$$anonfun$apply$1.apply(Action.scala:103) [play_2.11-2.4.2.jar:2.4.2]
at play.api.mvc.Action$$anonfun$apply$1.apply(Action.scala:96) [play_2.11-2.4.2.jar:2.4.2]
at play.api.libs.iteratee.Iteratee$$anonfun$mapM$1.apply(Iteratee.scala:524) [play-iteratees_2.11-2.4.2.jar:2.4.2]
at play.api.libs.iteratee.Iteratee$$anonfun$mapM$1.apply(Iteratee.scala:524) [play-iteratees_2.11-2.4.2.jar:2.4.2]
at play.api.libs.iteratee.Iteratee$$anonfun$flatMapM$1.apply(Iteratee.scala:560) [play-iteratees_2.11-2.4.2.jar:2.4.2]
at play.api.libs.iteratee.Iteratee$$anonfun$flatMapM$1.apply(Iteratee.scala:560) [play-iteratees_2.11-2.4.2.jar:2.4.2]
at play.api.libs.iteratee.Iteratee$$anonfun$flatMap$1$$anonfun$apply$13.apply(Iteratee.scala:536) [play-iteratees_2.11-2.4.2.jar:2.4.2]
at play.api.libs.iteratee.Iteratee$$anonfun$flatMap$1$$anonfun$apply$13.apply(Iteratee.scala:536) [play-iteratees_2.11-2.4.2.jar:2.4.2]
at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24) [scala-library-2.11.6.jar:na]
at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24) [scala-library-2.11.6.jar:na]
at akka.dispatch.TaskInvocation.run(AbstractDispatcher.scala:40) [akka-actor_2.11-2.3.11.jar:na]
at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:397) [akka-actor_2.11-2.3.11.jar:na]
at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260) [scala-library-2.11.6.jar:na]
at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339) [scala-library-2.11.6.jar:na]
at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979) [scala-library-2.11.6.jar:na]
at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107) [scala-library-2.11.6.jar:na]

Answer 1

我个人需要更多信息来调试此问题，但是，也许您可​​以根据我如何使用 Ebean 在 PostgreSQL 中存储和检索图像的示例获得继续所需的信息。

模型看起来像这样:

public class User extends Model {

    public static Finder<LInteger, User> find = new Finder<Integer,User>(User.class);

    @Id
    public Integer id;

    public String name;

    @Constraints.Required
    @Constraints.Email
    public String email;

    public String password;

    @Lob
    public byte[] photo;

    public static User findByEmail(String email) {
        return find.where().eq("email", email).findUnique();
    }

}

Controller 看起来像这样:

public class Application extends Controller {

    public static Result userPhoto(Integer userId) {
        User user = User.find.ById(userId);

        if (user == null) {
            return notFound();

        }

        if (user.photo == null) {
            return ok(Play.application().getFile("/public/images/default-user.jpg"), true).as("image/jpeg");
        }

        return ok(new ByteArrayInputStream(user.photo)).as("image/jpeg");
    }

}

希望这会有所帮助!