java - 无法实例化 javax.servlet.ServletException

Question

我正在尝试使用以下代码创建 javax.servlet.ServletException 类的实例

public class MyTroubleViewer {
 public static void main(String[] args) {
  javax.servlet.ServletException servletException = new javax.servlet.ServletException("Hello");
  System.out.println(servletException.getMessage());
 }
}

但是我在创建时遇到异常:

Exception in thread "main" java.lang.ClassFormatError: Absent Code attribute in method that is not native or abstract in class file javax/servlet/ServletException
...

Maven 帮助我处理依赖项:

<dependency>
 <groupId>javax</groupId>
 <artifactId>javaee-api</artifactId>
 <version>6.0</version>
 <type>jar</type>
 <scope>compile</scope>
</dependency>

我做错了什么？

Answer 1

如@user353852 所述，您当前的依赖项仅包含 Java EE 6 API，不包含任何方法体。所以你不能针对它运行代码。要在容器外运行代码，您需要获得“具体”依赖项(来自 GlassFish 存储库):

<repositories>
  <repository>
    <id>glassfish-repository</id>
    <url>http://download.java.net/maven/glassfish</url>
  </repository>
  ...
</repositories>

<dependencies>
  <dependency>
    <groupId>org.glassfish</groupId>
    <artifactId>javax.servlet</artifactId>
    <version>3.0</version>
    <scope>test</scope>
  </dependency>
  ...
</dependencies>

请注意，不应使用 compile 范围声明此类依赖项，您不想将其捆绑(它应该是 provided 或者 test ，但不是编译或运行时)。

---

I wonder does the provider of the javaee implementation important? Generally I use Apache servers, so it will be great to have the same javaee implementation as it is on the server.

理论上，不会。但在实践中，我建议使用来自您将要使用的服务器(或来自 Java EE 引用实现)的实现 JAR。由于您使用的是 Java EE 6，因此在这两种情况下，这实际上意味着来自 GlassFish v3 的 JARS。

The second question is much more vital. javax.servlet is only one part of javaee-api implementation, where can I find the others. Now I need "javax/validation/Validation".

对于 Bean Validation API，您需要以下内容(Hibernate Validator 是 RI):

<repositories>
  <!-- For Hibernate Validator -->
  <repository>
    <id>jboss</id>
    <name>JBoss repository</name>
    <url>http://repository.jboss.org/maven2</url>
  </repository>
  ...
</repositories>

<dependencies>
  <!-- Bean Validation API and RI -->
  <dependency>
    <groupId>javax.validation</groupId>
    <artifactId>validation-api</artifactId>
    <version>1.0.0.GA</version>
    <scope>provided</scope>
  </dependency>
  <dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-validator</artifactId>
    <version>4.0.2.GA</version>
    <scope>runtime</scope>
  </dependency>
  ...
</dependencies>

How can I determine which artifact implements each aspect of javaee. Maybe there is some kind of a "map" somewhere?

除this nice answer 外没有其他官方信息来自 BalusC 的帮助。