我希望能够将类实例保存到公共静态变量,但我无法弄清楚如何在Kotlin中执行此操作.

class Foo {

    public static Foo instance;
    public Foo() {
        instance = this;
    }

}

题

如何jdk.incubator.httpclient在运行时使模块中的类可见？

我在用什么

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

问题

=>使用时Maven构建失败jdk.incubator.HttpClient.修正了与这个问题由于@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> …

我在用什么

Java 9 + Maven + HttpClient(来自java 9) jdk.incubator.http.HttpClient

问题

使用maven构建项目时出现以下错误

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.7.0:compile (default-compile) on project Core: Compilation failure: Compilation failure:
[ERROR] Foo.java:[4,21] package jdk.incubator.http is not visible

第4行Foo是

import jdk.incubator.http.HttpClient;

的pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0">
<modelVersion>4.0.0</modelVersion>
<parent>
    <groupId>me.bar</groupId>
    <artifactId>foo</artifactId>
    <version>0.0.0-SNAPSHOT</version>
</parent>

<artifactId>Core</artifactId>

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


    <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> …