MessageDigest NoSuchAlgorithmException in Java

So, I’ve cruised through several Stackoverflow threads and other websites as well whilst trying to find a solution to this.

I am working on a school assignment that requires the use of an instance of MessageDigest.

I will paste my code below, but I have tried getInstance(“SHA-256”) and getInstance(“SHA-1”) and getInstance(“MD5”) all with the same error.

I have also tried adding the provider parameter with “SUN” but then I get a

NoSuchProviderException.

My school instructions call for import java.security.MessageDigest.

I have tried that as well as import java.security.* in case something was missing.

I have tried to get a list of providers but that does not give me anything and it won’t even compile.

I have followed the try/catch instructions found at this site. Still nothing.

I have no idea where to go next and none of the sites seems to have a solid answer for this.

According to Oracle, the process should cycle through providers until it finds one that supports whichever algorithm you selected, and I have tried all three on their list source.

I know it’s probably something super simple that I’m overlooking, but I can’t seem to get it straight. Any help would be appreciated. Code below

-Jon

Code:

package com.snhu.sslserver;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import java.security.MessageDigest;
import java.util.Scanner;

@SpringBootApplication
public class ServerApplication {

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

}

@RestController
class ServerController{
    
    //create instance of message digest
    MessageDigest md = MessageDigest.getInstance("SHA-256");
//FIXME:  Add hash function to return the checksum value for the data string that should contain your name.    
    @RequestMapping("/hash")
    public String myHash(){
        String data = "Hello Joe Smith!";
       
        return "<p>data:"+data;
    }
}

Answer

Independent Usage Issue

MessageDigest instances are not thread-safe. There is no thread-safety guarantee in the doc

Please do not use MessageDigest instance like this (unless your controller is request scoped)

Assumption

1. Thread pools are used by the server
2. Expectation is to reduce the overhead of MessageDigest object creation

Possible solution

1. Create ThreadLocal instance of MessageDigest
2. compute digest using this ThreadLocal instance
3. Hopefully future Fibers will honor this way of usage (if not, we have much bigger problem in java ecosystem)

Suggestion

In situations were threads are dynamically created/destroyed, and still the overhead of creating MessageDigest is considerable:

1. Manage a separate executor service(with threadpool), and manage digest using futures
2. or create new MessageDigest instance per request (to avoid unnecessary ThreadLocal overhead.