MethodArea.java

package com.coding.mini_jvm.src.com.coderising.jvm.engine;


import com.coding.mini_jvm.src.com.coderising.jvm.clz.ClassFile;
import com.coding.mini_jvm.src.com.coderising.jvm.constant.MethodRefInfo;
import com.coding.mini_jvm.src.com.coderising.jvm.loader.ClassFileLoader;
import com.coding.mini_jvm.src.com.coderising.jvm.method.Method;

import java.util.HashMap;
import java.util.Map;

public class MethodArea {

	public static final MethodArea instance = new MethodArea();

	/**
	 * 注意：我们做了极大的简化， ClassLoader 只有一个， 实际JVM中的ClassLoader,是一个双亲委托的模型
	 */

	private ClassFileLoader clzLoader = null;

	Map<String, ClassFile> map = new HashMap<String, ClassFile>();

	private MethodArea() {
	}

	public static MethodArea getInstance() {
		return instance;
	}

	public void setClassFileLoader(ClassFileLoader clzLoader) {
		this.clzLoader = clzLoader;
	}

	public Method getMainMethod(String className) {

		ClassFile clzFile = this.findClassFile(className);

		return clzFile.getMainMethod();
	}


	public ClassFile findClassFile(String className){
		
		if(map.get(className) != null){
			return map.get(className);
		}
		// 看来该class 文件还没有load过
		ClassFile clzFile = this.clzLoader.loadClass(className);
		map.put(className, clzFile);
		
		return clzFile;
		
	}
	
	
	public Method getMethod(String className, String methodName, String paramAndReturnType){
		ClassFile classFile = findClassFile(className);
		Method method = classFile.getMethod(methodName, paramAndReturnType);
		if (method == null) {
			throw new RuntimeException("method "+methodName+ "can't found");
		}
		return method;
	}
	
	
	public Method getMethod(MethodRefInfo methodRef){
		return getMethod(methodRef.getClassName(),
				methodRef.getMethodName(), methodRef.getParamAndReturnType());
	}
}