[JAVA] I tried to reduce the capacity of Spring Boot
Self-introduction
- opengl-8080 --Mainly writing technical memos in Qiita --Working at SIer in Kansai
What is Spring Boot?
--Mechanism / framework that makes it easy to create Spring-based applications --Build results are combined into a single jar file
Benefits of a single jar
--The AP server is included, so there is no need to prepare an AP server for each environment.
--The fun of starting with java -jar
Disadvantages of a single jar
--Since all dependent libraries including AP server are included, the file size becomes large.
I tried to reduce the jar size
result
result
Size comparison
How did you do it?
How do you do Hello World in Java?
1. 1. Write code
Hello.java
public class Hello {
public static void main(String... args) {
System.out.println("Hello World");
}
}
2. Compile with javac
$ javac Hello.java
3. 3. Hello.class is generated
4. Run in java
$ java Hello
Hello World
Did you understand?
The source code before compilation is smaller!
The API for hitting javac is standard!
https://docs.oracle.com/javase/jp/8/docs/api/javax/tools/JavaCompiler.html
How the improved jar works
|-LightweightJarExecutor.class :
|→ Code that extracts the source from its own jar, compiles and executes it
|-...
`-src/ :Spring Boot and a set of dependent library sources
|-ch/ : logback
|-com/ :jackson or com.like sun
|-javax/ :javaee standard API
|-META-INF/
|-org/ : Spring, hibernate, JBoss, Tomcat, etc...
`-sample/ :Spring MVC Hello World
Behavior at startup
- Extract the source code from your own jar and copy it to a temporary directory
- Compile the source output to the temporary directory using
JavaCompiler - Load the Spring Boot main class (
JarLauncher) from the output destination of the compilation result using ʻURLClassLoader`. - Execute the
main ()method ofJarLauncher
Just In Time Compile! (not) </ span>
If it is left as it is, it will be wasteful and cannot be reduced in weight.
Useless 1: Comment
Waste 2: Annotation
Waste 3: private
Waste 4: Blank + line feed
Wastefully sophisticated and lean code
Result Succeeded in reducing the capacity by 5MB! : grin :: thumbs up:
Compensation 1: Slow startup: innocent :: thumbsdown:
Compensation 2: Unable to debug: joy :: thumbsdown:
Please do not imitate a good child
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