java - 将 Javax 嵌入到 Java 9

Question

我花了好几个小时试图解决这个问题，我需要帮助:

这是一个众所周知的问题，javax 不是 java 9 的一部分，我不知道如何在没有以下异常的情况下运行它:

Exception in thread "main" org.hibernate.internal.util.config.ConfigurationException: Unable to perform unmarshalling at line number 0 and column 0 in FILE C:\Users\Miles\Workspace\Projekte\SpringProjekte\RestForFun\resources\hibernate.cfg.xml. Message: null
at org.hibernate.boot.cfgxml.internal.JaxbCfgProcessor.unmarshal(JaxbCfgProcessor.java:133)
at org.hibernate.boot.cfgxml.internal.JaxbCfgProcessor.unmarshal(JaxbCfgProcessor.java:65)
at org.hibernate.boot.cfgxml.internal.ConfigLoader.loadConfigXmlFile(ConfigLoader.java:76)
at org.hibernate.boot.registry.StandardServiceRegistryBuilder.configure(StandardServiceRegistryBuilder.java:167)
at org.hibernate.cfg.Configuration.configure(Configuration.java:300)
at noobz.teamz.RestForFun.RestForFunApplication.main(RestForFunApplication.java:31)
Caused by: javax.xml.bind.JAXBException: Implementation of JAXB-API has not been found on module path or classpath.
 - with linked exception:
[java.lang.ClassNotFoundException: com.sun.xml.internal.bind.v2.ContextFactory]
at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:278)
at javax.xml.bind.ContextFinder.find(ContextFinder.java:421)
at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:721)
at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:662)
at org.hibernate.boot.cfgxml.internal.JaxbCfgProcessor.unmarshal(JaxbCfgProcessor.java:122)
... 5 more
Caused by: java.lang.ClassNotFoundException: com.sun.xml.internal.bind.v2.ContextFactory
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:582)
at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:185)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:496)
at javax.xml.bind.ServiceLoaderUtil.nullSafeLoadClass(ServiceLoaderUtil.java:122)
at javax.xml.bind.ServiceLoaderUtil.safeLoadClass(ServiceLoaderUtil.java:155)
at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:276)
... 9 more

这是我的例子:

import org.hibernate.cfg.Configuration;
import java.io.*;


public class RestForFunApplication {


    public static void main(String[] args) {


        RestForFunApplication rsf = new RestForFunApplication();

        File file = new File("resources\\hibernate.cfg.xml");
        if (!file.exists())
            System.out.println("no hibernate.cfg.xml");
        Configuration sessionFactory = new Configuration();
        sessionFactory.configure(file);
    }
}

这是我的 pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>noobz.teamz</groupId>
<artifactId>RestForFun</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>

<name>RestForFun</name>
<description>Demo project for Spring Boot</description>

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.9.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <java.version>1.8</java.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <dependency>
        <groupId>org.postgresql</groupId>
        <artifactId>postgresql</artifactId>
        <version>42.1.4</version>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-entitymanager</artifactId>
        <version>5.2.12.Final</version>
    </dependency>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-validator</artifactId>
        <version>6.0.7.Final</version>
    </dependency>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-search</artifactId>
        <version>5.8.2.Final</version>
    </dependency>
    <dependency>
        <groupId>javax.inject</groupId>
        <artifactId>javax.inject</artifactId>
        <version>1</version>
    </dependency>
    <dependency>
        <groupId>javax.xml.bind</groupId>
        <artifactId>jaxb-api</artifactId>
        <version>2.3.0</version>
    </dependency>
    <dependency>
        <groupId>org.glassfish.jaxb</groupId>
        <artifactId>jaxb-core</artifactId>
        <version>2.3.0</version>
    </dependency>
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.6.2</version>
            <configuration>
                <release>9</release>
                <compilerArgs>
                    <arg>--add-modules</arg>
                    <arg>javax.xml.bind</arg>
                </compilerArgs>
            </configuration>
        </plugin>
    </plugins>
</build>

这是我的 hibernate.cfg.xml

<hibernate-configuration>
<session-factory>
    <property name="hibernate.connection.driver_class">org.postgresql.Driver</property>
    <property name="hibernate.connection.url">db</property>
    <property name="hibernate.connection.username">usr</property>
    <property name="hibernate.connection.password">psswrd</property>
    <property name="hibernate.dialect">org.hibernate.dialect.PostgreSQL94Dialect</property>
    <property name="connection.pool_size">1</property>
</session-factory>

我加了

--add-modules=java.xml.bind,java.activation

和

--add-modules java.se.ee

到 intellij idea 编译器设置，还尝试通过控制台运行。

没有任何效果，我仍然得到异常。我快哭了，完成这项工作非常必要。

Answer 1

这是个好问题。但它可以简化为非常短的示例，因此您无需为 spring 或 hibernate 依赖项打扰读者。已经是这个简短的代码:

public static void main(String[] args) throws Exception {
    JAXBContext jaxbContext = JAXBContext.newInstance(Foo.class);
}

会导致问题(考虑 Foo 是任何 POJO)。

事实上，S.O. 上所有现存的解决方案。这说明这个问题不能正常工作(例如，这个“规范”问题:How to resolve java.lang.NoClassDefFoundError: javax/xml/bind/JAXBException in Java 9)。我不知道这是最近 Java JDK (9.0.1) 的一些更新的结果，还是我做错了。然而。我个人认为使用 --add-module 属性不是一种干净的方式。我相信，正确的方法是只使用 Maven 依赖项。我发现了这个所需的最小列表，它是:

<dependencies>
    <dependency>
        <groupId>javax.xml.bind</groupId>
        <artifactId>jaxb-api</artifactId>
        <version>2.3.0</version>
    </dependency>
    <dependency>
        <groupId>com.sun.xml.bind</groupId>
        <artifactId>jaxb-impl</artifactId>
        <version>2.3.0</version>
    </dependency>
    <dependency>
        <groupId>org.glassfish.jaxb</groupId>
        <artifactId>jaxb-runtime</artifactId>
        <version>2.3.0</version>
    </dependency>
    <dependency>
        <groupId>javax.activation</groupId>
        <artifactId>activation</artifactId>
        <version>1.1.1</version>
    </dependency>
</dependencies>

因此您不需要再显式指定--add-module，只需将其删除即可。

---

附言在您的特定代码中，还请修复此属性:

<java.version>1.8</java.version>

当您使用 Java-9 时。