使模块 jdk.incubator.httpclient 在运行时可见

Question

问题

如何使模块jdk.incubator.httpclient 中的类在运行时可见？

我在用什么

Java 9 + Maven + HttpClient jdk.incubator.http.HttpClient

问题

=> 使用 jdk.incubator.HttpClient 时 Maven 构建失败。 修复 this question 感谢@nullpointer

=> 运行时堆栈跟踪：

java.lang.NoClassDefFoundError: jdk/incubator/http/HttpClient
at com.foo.Bar.Bar.<clinit>(Bar.java:56) ~[?:?]
at java.lang.Class.forName0(java.base@9-Ubuntu/Native Method) ~[?:?]
at java.lang.Class.forName(java.base@9-Ubuntu/Class.java:374) ~[?:?]
Caused by: java.lang.ClassNotFoundException: jdk.incubator.http.HttpClient
at java.net.URLClassLoader.findClass(java.base@9-Ubuntu/URLClassLoader.java:388) ~[?:?]
at java.lang.ClassLoader.loadClass(java.base@9-Ubuntu/ClassLoader.java:486) ~[?:?]
at java.lang.ClassLoader.loadClass(java.base@9-Ubuntu/ClassLoader.java:419) ~[?:?]
at com.foo.Bar.Bar.<clinit>(Bar.java:56) ~[?:?]
at java.lang.Class.forName0(java.base@9-Ubuntu/Native Method) ~[?:?]
at java.lang.Class.forName(java.base@9-Ubuntu/Class.java:374) ~[?:?]

构建 Pom 部分

<build>
    <finalName>${project.artifactId}</finalName>
    <sourceDirectory>${project.basedir}/src</sourceDirectory>

    <resources>
        <resource>
            <targetPath>.</targetPath>
            <filtering>true</filtering>
            <directory>${project.basedir}/resources</directory>

            <includes>
                <include>plugin.yml</include>
            </includes>
        </resource>
    </resources>

    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-clean-plugin</artifactId>
            <version>3.0.0</version>
        </plugin>

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.7.0</version>

            <configuration>
                <source>9</source>
                <target>9</target>
            </configuration>
        </plugin>

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-shade-plugin</artifactId>
            <version>3.1.0</version>

            <executions>
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>shade</goal>
                    </goals>
                    <configuration>
                        <minimizeJar>true</minimizeJar>
                    </configuration>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

如您所见，我使用 maven-shade-plugin 作为我的依赖项，但由于 jdk.incubator.http.HttpClient 是 JDK 的一部分，它不包含在我的 jar 中。

尝试执行为：

 java -jar --add-modules jdk.incubator.httpclient uhc-staging.jar

导致以下异常：

Error occurred during initialization of VM 
java.lang.module.ResolutionException: Module jdk.incubator.httpclient not found 
at java.lang.module.Resolver.fail(java.base@9-Ubuntu/Resolver.java:790) 
at java.lang.module.Resolver.resolveRequires(java.base@9-Ubuntu/Resolver.java:94)
at java.lang.module.Configuration.resolveRequiresAndUses(java.base@9-Ubuntu/Configuration.java:370)
at java.lang.module.ModuleDescriptor$1.resolveRequiresAndUses(java.base@9-Ubuntu/ModuleDescriptor.java:1986)
at jdk.internal.module.ModuleBootstrap.boot(java.base@9-Ubuntu/ModuleBootstrap.java:263)
at java.lang.System.initPhase2(java.base@9-Ubuntu/System.java:1927)

Answer 1

在discussion中，带出的细节是执行：-

java --list-modules

不包含 jdk.incubator.httpclient 作为模块，这就是抛出 j.l.m.ResolutionException 的原因。因此，解决方案是将安装的 JDK 版本升级到最新版本（应包括孵化器模块），然后尝试使用与建议相同的命令运行应用程序：-

java -jar --add-modules jdk.incubator.httpclient uhc-staging.jar