Java 在 运行 jar 时找不到 jar 中的属性文件

Question

当我从 IntelliJ 得到 运行 main() 时，我预期 peter,johnson 作为标准输出的结果。但是当我 运行 mvn clean package 并尝试执行 java -jar target/example-1.0.0-SNAPSHOT-jar-with-dependencies.jar 时，我收到以下错误消息。为什么以及如何确保读取 .properties 文件？

java -jar target/example-1.0.0-SNAPSHOT-jar-with-dependencies.jar
Exception in thread "main" java.io.FileNotFoundException:      file:/Users/ismar.slomic/src/ADOP/example/target/example-1.0.0-SNAPSHOT-  jar-with-dependencies.jar!/my-example.properties (No such file or   directory)
at java.io.FileInputStream.open0(Native Method)
at java.io.FileInputStream.open(FileInputStream.java:195)
at java.io.FileInputStream.<init>(FileInputStream.java:138)
at java.io.FileInputStream.<init>(FileInputStream.java:93)
at com.example.MyPropertiesClass.getFullName(MyPropertiesClass.java:18)
at com.example.MyMainClass.main(MyMainClass.java:9)

MyMainClass

package com.example;

import java.io.IOException;

public class MyMainClass {

   public static void main(String[] args) throws IOException {
       MyPropertiesClass mpc = new MyPropertiesClass();
       System.out.println(mpc.getFullName());
   }
}

我的属性类

package com.example;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Properties;

public class MyPropertiesClass {

  public String getFullName() throws IOException {
    Properties properties = new Properties();
    ClassLoader cl = this.getClass().getClassLoader();
    String filePath = cl.getResource("my-example.properties").getFile();

    BufferedInputStream bis = new BufferedInputStream(new FileInputStream(filePath));
    properties.load(bis);

    String name = properties.getProperty("name");
    String lastname = properties.getProperty("lastname");
    return name + "," + lastname;
  }
}

我的-example.properties

name=peter
lastname=johnson

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns="http://maven.apache.org/POM/4.0.0"
     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.example</groupId>
<artifactId>example</artifactId>
<version>1.0.0-SNAPSHOT</version>

<name>${project.artifactId}</name>
<description>My Example</description>

<properties>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>

<build>
    <plugins>
        <plugin>
            <artifactId>maven-assembly-plugin</artifactId>
            <version>3.0.0</version>
            <configuration>
                <descriptorRefs>
                    <descriptorRef>jar-with-dependencies</descriptorRef>
                </descriptorRefs>
                <archive>
                    <manifest>
                        <addClasspath>true</addClasspath>
                        <classpathPrefix>lib/</classpathPrefix>
                        <mainClass>com.example.MyMainClass</mainClass>
                    </manifest>
                </archive>
            </configuration>
            <executions>
                <execution>
                    <id>make-assembly</id>
                    <phase>package</phase>
                    <goals>
                        <goal>single</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>

Answer 1

如果您的 属性 文件在您的 jar 中，那么您最好使用 getResourceAsStream 而不是 getResource 和 getFile.

类似于：

  ClassLoader cl = this.getClass().getClassLoader();
  try (InputStream stream = cl.getResourceAsStream("my-example.properties")) {
     properties.load(bis);
  }

方法 getResource(String)returns URL 指向 jar 中的文件。在您的情况下，类似于：file:/Users/ismar.slomic/src/ADOP/example/target/example-1.0.0-SNAPSHOT-jar-with-dependencies.jar!/my-example.properties。当您在 URL 上调用 getFile 时，它 returns 文件（即 jar）而不是指向内部属性文件的指针。

也可以在 URL 上打开一个连接并使用返回的 JarURLConnection。但是 getResourceAsStream.

更容易