ClassFileLoader.java

package task7.jvm.loader;

import org.apache.commons.io.IOUtils;
import org.apache.commons.lang3.StringUtils;
import task7.jvm.clz.ClassFile;

import java.io.*;
import java.util.ArrayList;
import java.util.List;

public class ClassFileLoader {

    private List<String> clzPaths = new ArrayList<String>();

    public byte[] readBinaryCode(String className) {

        className = className.replace('.', File.separatorChar) + ".class";

        for (String path : this.clzPaths) {

            String clzFileName = path + File.separatorChar + className;
            byte[] codes = loadClassFile(clzFileName);
            if (codes != null) {
                return codes;
            }
        }
        return null;
    }

    private byte[] loadClassFile(String clzFileName) {

        File f = new File(clzFileName);

        try {

            return IOUtils.toByteArray(new FileInputStream(f));

        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }


    public void addClassPath(String path) {
        if (this.clzPaths.contains(path)) {
            return;
        }

        this.clzPaths.add(path);

    }


    public String getClassPath() {
        return StringUtils.join(this.clzPaths, ";");
    }

    public ClassFile loadClass(String className) {
        byte[] codes = this.readBinaryCode(className);
        ClassFileParser parser = new ClassFileParser();
        return parser.parse(codes);

    }


    // ------------------------------backup------------------------
    public String getClassPath_V1() {

        StringBuffer buffer = new StringBuffer();
        for (int i = 0; i < this.clzPaths.size(); i++) {
            buffer.append(this.clzPaths.get(i));
            if (i < this.clzPaths.size() - 1) {
                buffer.append(";");
            }
        }
        return buffer.toString();
    }

    private byte[] loadClassFile_V1(String clzFileName) {

        BufferedInputStream bis = null;

        try {

            File f = new File(clzFileName);


            bis = new BufferedInputStream(new FileInputStream(f));

            ByteArrayOutputStream bos = new ByteArrayOutputStream();


            byte[] buffer = new byte[1024];
            int length = -1;

            while ((length = bis.read(buffer)) != -1) {
                bos.write(buffer, 0, length);
            }

            byte[] codes = bos.toByteArray();

            return codes;

        } catch (IOException e) {
            e.printStackTrace();

        } finally {
            if (bis != null) {
                try {
                    bis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return null;

    }


}