[Solved] You wrote this Dockerfile snippet: FROM maven:3.8.6-openjdk-17 AS builder WORKDIR /app COPY . . RUN mvn package FROM openjdk:17-jdk-slim COPY /app/target/app.jar /app/app.... | Spring Boot

Spring Boot - Docker and Deployment

You wrote this Dockerfile snippet:

FROM maven:3.8.6-openjdk-17 AS builder
WORKDIR /app
COPY . .
RUN mvn package

FROM openjdk:17-jdk-slim
COPY /app/target/app.jar /app/app.jar
ENTRYPOINT ["java", "-jar", "/app/app.jar"]

The build fails with 'COPY failed: stat /app/target/app.jar: no such file or directory'. What is the error?

AMaven package command failed silently

BCOPY source path is incorrect; should use --from=builder

CENTRYPOINT syntax is invalid

DWORKDIR is missing in second stage

Step-by-Step Solution

Solution:

Step 1: Identify COPY source in second stage
The COPY command tries to copy from local /app/target/app.jar, which does not exist in second stage context.
Step 2: Correct usage for multi-stage copy
Must specify --from=builder to copy from build stage's filesystem.
Final Answer:
COPY source path is incorrect; should use --from=builder -> Option B
Quick Check:
COPY without --from in multi-stage = error [OK]

Quick Trick: Use COPY --from=builder to access build stage files [OK]

Common Mistakes:

Forgetting --from=builder in COPY
Assuming files persist between stages without COPY
Ignoring build errors in Maven package

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You wrote this Dockerfile snippet:

Step 1: Identify COPY source in second stage

Step 2: Correct usage for multi-stage copy

Final Answer:

Quick Check:

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