[Solved] You wrote this in application.properties:server.port9090Why does your Spring Boot app fail to start on port 9090? | Spring Boot

Spring Boot - Application Configuration

You wrote this in application.properties:

server.port9090

Why does your Spring Boot app fail to start on port 9090?

ASpaces are not allowed anywhere in properties files.

BPort 9090 is reserved and cannot be used.

CMissing equals sign between key and value causes syntax error.

DProperty name is incorrect; should be server.port.number.

Step-by-Step Solution

Solution:

Step 1: Check properties file syntax
Each line must have a key and value separated by an equals sign (=) or colon (:).
Step 2: Identify the missing equals sign
The line server.port9090 lacks the equals sign, causing it to be parsed as a single key with no value and preventing the port from being set.
Final Answer:
Missing equals sign between key and value causes syntax error. -> Option C
Quick Check:
Properties need key=value format [OK]

Quick Trick: Always use = or : between key and value [OK]

Common Mistakes:

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