運行jar時找不到jar中的Java屬性文件

Question

當我從IntelliJ運行main() ，得到的結果是標准的peter,johnson 。 但是，當我運行mvn clean package並嘗試執行java -jar target/example-1.0.0-SNAPSHOT-jar-with-dependencies.jar以下錯誤消息。 為什么以及如何確保讀取.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());
   }
}

MyPropertiesClass

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;
  }
}

my-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

如果屬性文件在jar中，則最好使用getResourceAsStream而不是getResource和getFile 。

就像是：

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

方法getResource(String)返回指向jar內文件的URL。 在您的情況下，類似於： file:/Users/ismar.slomic/src/ADOP/example/target/example-1.0.0-SNAPSHOT-jar-with-dependencies.jar!/my-example.properties 。 當您在該URL上調用getFile時，它將返回文件（即jar），而不是指向內部屬性文件的指針。

也可以使用URL打開連接並使用返回的JarURLConnection 。 但是使用getResourceAsStream更容易。