com.github.netty.core.util.ClassFileMethodToParameterNamesFunction Maven / Gradle / Ivy

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package com.github.netty.core.util;

import java.io.IOException;
import java.lang.instrument.IllegalClassFormatException;
import java.lang.reflect.Member;
import java.lang.reflect.Method;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Function;

/**
 * read class file - based method variable parameter name function
 *
 * @author wangzihao
 */
public class ClassFileMethodToParameterNamesFunction implements Function {
    private static final String[] EMPTY = {};
    private static LoggerX logger = LoggerFactoryX.getLogger(ClassFileMethodToParameterNamesFunction.class);
    private final Map, Map> parameterNamesCache = new ConcurrentReferenceHashMap<>(
            16, ConcurrentReferenceHashMap.ReferenceType.WEAK);

    public static Map readParameterNameMap(Class clazz) {
        try {
            JavaClassFile javaClassFile = new JavaClassFile(clazz);
            Map result = new HashMap<>(6);
            for (JavaClassFile.Member member : javaClassFile.getMethods()) {
                try {
                    Member javaMember = member.toJavaMember();
                    String[] parameterNames = member.getParameterNames();
                    result.put(javaMember, parameterNames);
                } catch (Exception e) {
                    logger.warn("readParameterNameMap member = {}, error = {}", member, e.toString());
                }
            }
            return result;
        } catch (ClassNotFoundException | IOException | IllegalClassFormatException e) {
            return Collections.emptyMap();
        }
    }

    public static void main(String[] args) {
        Map memberMap = readParameterNameMap(ClassFileMethodToParameterNamesFunction.class);
        System.out.println("memberMap = " + memberMap);
    }

    @Override
    public String[] apply(Method method) {
        Class declaringClass = method.getDeclaringClass();
        if (declaringClass.isInterface()) {
            return EMPTY;
        }
        Map memberMap = parameterNamesCache.get(declaringClass);
        if (memberMap == null) {
            memberMap = readParameterNameMap(declaringClass);
            parameterNamesCache.put(declaringClass, memberMap);
        }
        String[] parameterNames = memberMap.get(method);
        if (parameterNames == null) {
            throw new IllegalStateException("bad method!. object=" + method.getDeclaringClass() + ",method=" + method);
        }
        return parameterNames;
    }
}