Question

我在Eclipse中有简单的maven项目。该应用程序包含文件：src / main / resources / test.txt。我想读取文件并将其写在输出上。它可以在Eclipse中运行，但在创建jar文件后不能从命令行运行。如何配置项目以两种方式工作。我哪里错了？不正确的jar文件，java代码，清单，maven配置？

申请结构：

Application structure

运行：

java -jar fileRead-0.0.1-SNAPSHOT.jar

错误：

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/io/IOUtils
    at fileRead.FileRead.main(FileRead.java:11)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.io.IOUtils
        at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        ... 1 more

Java代码：

package fileRead;
import java.io.IOException;

import org.apache.commons.io.IOUtils;

public class FileRead {
    public static void main(String[] args) {
    String file = null;
    try {
        file = IOUtils.toString((new FileRead()).getClass().getClassLoader().getResourceAsStream("test.txt"));
    } catch (IOException e) {
        e.printStackTrace();
    }
    System.out.println(file);
    }
}

的pom.xml：

<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>com.fileRead</groupId>
<artifactId>fileRead</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>fileRead</name>
<url>http://maven.apache.org</url>
<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.target>1.8</maven.compiler.target>
    <maven.compiler.source>1.8</maven.compiler.source>
</properties>
<dependencies>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.apache.directory.studio</groupId>
        <artifactId>org.apache.commons.io</artifactId>
        <version>2.4</version>
    </dependency>
</dependencies>
<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jar-plugin</artifactId>
            <version>3.0.2</version>
            <configuration>
                <archive>
                    <manifest>
                        <addClasspath>true</addClasspath>
                        <mainClass>fileRead.FileRead</mainClass>
                    </manifest>
                </archive>
            </configuration>
        </plugin>
    </plugins>
</build>

FILEREAD-0.0.1-SNAPSHOT.jar：

fileRead
    FileRead.class
META-INF
    maven
    MANIFEST.MF
    test.txt

MANIFEST.MF：

Manifest-Version: 1.0
Built-By: msmorenda
Class-Path: org.apache.commons.io-2.4.jar commons-io-2.4.jar
Created-By: Apache Maven 3.5.0
Build-Jdk: 1.8.0_121
Main-Class: fileRead.FileRead

的test.txt：

abc
def
ghi

Answer 1

问题是MANIFEST.MF指向所需的依赖项。但是依赖项与生成的jar文件不在同一目录中。要复制所需的库（commons-io），您需要在pom中添加另一个插件，如下所示：

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-dependency-plugin</artifactId>
    <executions>
        <execution>
            <id>copy-dependencies</id>
            <phase>prepare-package</phase>
            <goals>
                <goal>copy-dependencies</goal>
            </goals>
            <configuration>
                <outputDirectory>${project.build.directory}/lib</outputDirectory>
            </configuration>
        </execution>
    </executions>
</plugin>

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-jar-plugin</artifactId>
    <version>3.0.2</version>
    <configuration>
        <archive>
            <manifest>
                <classpathPrefix>lib</classpathPrefix>
                <addClasspath>true</addClasspath>
                <mainClass>fileread.FileRead</mainClass>
            </manifest>
        </archive>
    </configuration>
</plugin>

具有上述配置的maven-dependency-plugin将在lib下的target目录中复制所需的库。现在，如果您将target目录设为当前目录并调用java -jar <name_of_jar>，则一切都应该有效。

注意：如果您想将jar文件移动到另一个位置，则应将其与lib目录一起打包。另请注意，我将您的课程的名称更改为fileread而不是fileRead。原因？ Java惯例。

Answer 2

您可以使用maven创建一个包含所需库的程序集，然后使用“mvn package”创建它

的pom.xml

<build>
    <plugins>
        <plugin>
            <artifactId>maven-assembly-plugin</artifactId>
            <version>2.6</version>
            <configuration>
                <descriptors>
                    <descriptor>src/assemblies/bin-with-dependencies.xml</descriptor>
                </descriptors>
                <tarLongFileMode>gnu</tarLongFileMode>
            </configuration>
        </plugin>
    </plugins>
</build>

的src /组件/ bin中与 - dependencies.xml

<assembly>
    <id>bin-with-dependencies</id>
    <formats>
        <format>jar</format>
    </formats>
    <includeBaseDirectory>false</includeBaseDirectory>
    <dependencySets>
        <dependencySet>
            <outputDirectory></outputDirectory>
            <unpack>false</unpack>
            <scope>compile</scope>
        </dependencySet>
        <dependencySet>
            <unpack>false</unpack>
            <scope>runtime</scope>
            <useProjectArtifact>true</useProjectArtifact>
        </dependencySet>
    </dependencySets>
</assembly>

这创建并存档包含jar和其所有库的文件夹然后像

一样运行它

java -cp {directory_jars} / * fileread.FileRead ...

“/ *”可能仅适用于Windows

通过maven创建jar以从同一个jar文件中读取资源文本文件

2 个答案: