Generating and compiling runtime code

Question

Let's say I have this code that uses some input (like a URL path) to determine which method to run, via reflection:

// init
map.put("/users/*", "viewUser");
map.put("/users", "userIndex");

// later
String methodName = map.get(path);
Method m = Handler.class.getMethod(methodName, ...);
m.invoke(handler, ...);

This uses reflection, so performance can be improved. This can be done as follows:

// init
map.put("/users/*", new Runnable() { public void run() { handler.viewUser(); } });
map.put("/users", new Runnable() { public void run() { handler.userIndex(); } });

// later
Runnable action = map.get(path);
action.run();

But for manually creating all of these Runnable, as this has its problems. I am wondering if I can create them at runtime? Therefore, I will have an input map, as in the first example, and will dynamically create a map of the second example. Of course, generation is just a matter of constructing a string, but what about compiling and loading it?

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Answer 1

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Answer 2

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Answer 3

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Answer 4

Well, you can write the code in a .java file, compile it using javac ( how to do it ), and load it into Java using Reflection.

But perhaps, as a compromise, you can also get Method objects during initialization - so you just need to call the invoke () method for each request.