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Spring Boot: URL to file in src/main/resources not found in Docker container

I have a Spring Boot backend application which has following part in the application.properties:

token.json_file_url=${TOKEN_JSON_FILE_URL:file:src/main/resources/localdev/user-claims.json}

${TOKEN_JSON_FILE_URL} env variable is not set, so the default file:src/main/… is in effect.

In a bundled library it’s used like this when a REST call is made:

@Value("${token.json_file_url}")
private String userClaimsTokenJsonFileUrl;
...
ObjectMapper objectMapper = new ObjectMapper(); //Jackson
Map<String, Object> map =
objectMapper.readValue(new URL(this.userClaimsTokenJsonFileUrl), new TypeReference<Map<String, Object>>() {});

Now executing the fat-jar generated by spring-boot-maven plugin runs perfectly fine in console via java -jar the-app.jar.

But copying the same jar into a docker container and firing a REST call against that yields a

java.io.FileNotFoundException: src/main/resources/localdev/user-claims.json.

How can that be?

To be complete, here’s the Dockerfile:

FROM amazoncorretto:17-alpine
ARG JAR_FILE=target/*.jar
COPY ${JAR_FILE} app/the-app.jar
WORKDIR /app
EXPOSE 8080
CMD ["java", "-Djava.security.egd=file:/dev/./urandom", "-jar", "the-app.jar"]

I also extracted the jar inside the container and the structure is:
BOOT-INF/classes/localdev/user-claims.json

It’s there. It just can’t be found running in a Docker container as opposed to running my jar locally.

Any ideas?

Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    OK so actually the problem was much more stupid than I realised...

    I was executing the JAR from my root project directory. Like java -jar target/the-app.jar.

    What I didn't realize was that the path root/src/main/resources/localdev/... was available to the code running in the jar... It was not using the packed resources INSIDE the jar, but the external files...

    That's why the

    new URL(file:src/main/resources/...)

    worked for the jar, while of course in the Docker container, this path wasn't there.

    Again, my mistake was that I thought the JAR used the resources packed inside the JAR, which it did not!

    Fixed it by copying the files also into the Docker container.


  2. 0

    Project Tree

    demo-springboot-json-app
├── Dockerfile
├── my-docker-data
│   └── token-003.json
├── pom.xml
├── src
│   └── main
│       ├── java
│       │   └── com
│       │       └── example
│       │           └── demo
│       │               ├── DemoApplication.java
│       │               └── HelloController.java
│       └── resources
│           ├── application.properties
│           ├── logback.xml
│           └── token-001.json
└── token-002.json

    Test JSON

    token-001.json

    {
    "token": "AAAA",
    "expiresIn": 1100
}

    token-002.json

    {
    "token": "BBBB",
    "expiresIn": 2200
}

    token-003.json

    {
    "token": "CCCC",
    "expiresIn": 3300
}

    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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.2.8</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>demo-springboot-json-app</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo-springboot-json-app</name>
    <description>demo-springboot-json-app project for Spring Boot</description>

    <properties>
        <maven.compiler.source>17</maven.compiler.source>
        <maven.compiler.target>17</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-logging</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

    application.properties

    spring.application.name=demo

token.json_file_url=${TOKEN_JSON_FILE_URL:token-001.json}

    logback.xml

    <?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <appender name="Console" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d [%thread] %-5level %-50logger{40} - %msg%n</pattern>
        </encoder>
    </appender>
     
    <appender name="RollingFile" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>app.log</file>
        <encoder>
            <pattern>%d [%thread] %-5level %-50logger{40} - %msg%n</pattern>
        </encoder>
         
        <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
            <fileNamePattern>app-%d{yyyy-MM-dd}.%i.log</fileNamePattern>
            <maxFileSize>1MB</maxFileSize>
            <maxHistory>30</maxHistory>
            <totalSizeCap>10MB</totalSizeCap>
            <cleanHistoryOnStart>true</cleanHistoryOnStart>
        </rollingPolicy>
    </appender>
     
    <root level="INFO">
        <appender-ref ref="Console" />
        <appender-ref ref="RollingFile" />
    </root>
</configuration>

    DemoApplication.java

    package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

}

    HelloController.java

    package com.example.demo;

import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.core.io.ClassPathResource;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.Map;
import java.net.URL;

@RestController
public class HelloController {

    private static final Logger logger = LoggerFactory.getLogger(HelloController.class);

    @Value("${token.json_file_url}")
    private String userClaimsTokenJsonFileUrl;


    @GetMapping("/hello2/{name}")
    public String sayHello2(
            @PathVariable String name,
            @RequestParam(value = "greeting", defaultValue = "Hello") String greeting
    ) {

        logger.info(">>>> Token JSON File: {}", userClaimsTokenJsonFileUrl);

        ObjectMapper objectMapper = new ObjectMapper();
        Map<String, Object> map = null;
                
        File file = new File(userClaimsTokenJsonFileUrl);
        if (file.exists()) {
            try {
                map = objectMapper.readValue(file, new TypeReference<Map<String, Object>>() {
                });
            } catch (IOException ex) {
                throw new RuntimeException(ex);
            }
        } else {
            ClassPathResource resource = new ClassPathResource(userClaimsTokenJsonFileUrl);
            try ( InputStream inputStream = resource.getInputStream()) {
                {
                    if (inputStream == null) {
                        String errMsg = "File not found in classpath or file system: " + userClaimsTokenJsonFileUrl;
                        logger.error("{}", errMsg);
                        throw new IllegalArgumentException(errMsg);
                    }
                    map = objectMapper.readValue(inputStream, new TypeReference<Map<String, Object>>() {
                    });
                }
            } catch (IOException ex) {
                logger.error("{}", ex);
                throw new RuntimeException(ex);
            }
        }

        if (map != null) {
            String token = (String) map.get("token");
            String expiresIn = String.valueOf(map.get("expiresIn"));
            logger.info(">>>> Token: " + token);
            logger.info(">>>> Expires In: " + expiresIn);
        } else {
            logger.error("CAN NOT READ MAP");
        }


        String msg = String.format("%s, %s!", greeting, name);
        logger.info(">>>> {} ", msg);
        return msg;
    }
    
}

    Dockerfile

    # Build
FROM maven:3.9.5-eclipse-temurin-17-alpine AS build
WORKDIR /BUILDTMP
COPY pom.xml .
COPY src ./src
RUN mvn clean package -DskipTests

# Runtime
FROM amazoncorretto:17-alpine
ARG JAR_FILE=my-app.jar

WORKDIR /app
COPY --from=build /BUILDTMP/target/${JAR_FILE} ./app.jar

EXPOSE 8080

CMD ["java", "-Djava.security.egd=file:/dev/./urandom", "-jar", "app.jar"]

    Build and Run

    Build

    mvn clean package

    Run

    Terminal-1

    java -jar target/demo-springboot-json-app-0.0.1-SNAPSHOT.jar

    Test-1

    Terminal-2

    curl http://localhost:8080/hello2/ABCD12345678

    check Terminal-1 console output

    >>>> Token JSON File: token-001.json
>>>> Token: AAAA
>>>> Expires In: 1100

    App read jar file’s token-001.json success.(Read file from classpath resource)

    In Terminal-1 , Ctrl + C , Stop App.

    Test-2 Set Environment

    Terminal-1

    export TOKEN_JSON_FILE_URL=token-002.json

java -jar target/demo-springboot-json-app-0.0.1-SNAPSHOT.jar

    Terminal-2

    curl http://localhost:8080/hello2/ABCD12345678

    check Terminal-1 console output

    >>>> Token JSON File: token-002.json
>>>> Token: BBBB
>>>> Expires In: 2200

    App read token-002.json success.(Read file from Environment Config)

    In Terminal-1 , Ctrl + C , Stop App.

    Build Docker Container

    docker build 
  --build-arg JAR_FILE=demo-springboot-json-app-0.0.1-SNAPSHOT.jar 
  -t my-app-image .

    Docker Test-1

    Terminal-1

    docker run -it -p 8080:8080 my-app-image

    Terminal-2

    curl http://localhost:8080/hello2/ABCD12345678

    check Terminal-1 console output

    >>>> Token JSON File: token-001.json
>>>> Token: AAAA
>>>> Expires In: 1100

    App read jar file’s token-001.json success.(Read file from classpath resource)

    In Terminal-1 , Ctrl + C , Stop App.

    Docker Test-2 Set Environment

    Terminal-1

    docker run -it 
  -p 8080:8080 
  -v `pwd`/my-docker-data:/conf 
  -e TOKEN_JSON_FILE_URL=/conf/token-003.json 
  my-app-image

    Terminal-2

    curl http://localhost:8080/hello2/ABCD12345678

    check Terminal-1 console output

    >>>> Token JSON File: /conf/token-003.json
>>>> Token: CCCC
>>>> Expires In: 3300

    App read token-003.json success.(Read file from Environment Config)

    In Terminal-1 , Ctrl + C , Stop App.

    Another Solution About Read File

    I did not use the following writing method. The following writing method may be what you want:

        public InputStream loadFile(String path) throws Exception {
        URL url;
        
        //Read From Internet
        if (path.startsWith("http://") || path.startsWith("https://")) {
            url = new URL(path);
        } 

        //Read From Local File
        else if (path.startsWith("file:/")) {
            url = new URL(path);
        } 

        else {
        
        //Read From Classpath
        
            ClassLoader classLoader = getClass().getClassLoader();
            url = classLoader.getResource(path);
            if (url == null) {
                throw new IllegalArgumentException("File not found in classpath: " + path);
            }
        }
        
        return url.openStream();
    }

    application.properties

    # Read From Classpath File
token.json_file_url=${TOKEN_JSON_FILE_URL:token-001.json}

# Read From Local File
token.json_file_url=${TOKEN_JSON_FILE_URL:file:///path/to/your/token-002.json}

# Read From Internet File
token.json_file_url=${TOKEN_JSON_FILE_URL:http://hello.world.com/token-003.json}
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