jni 加载本地dll类库

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.text.SimpleDateFormat;
import java.util.Date;


public class JniLibrary {

    static final String SEPARATOR;

    static {
        SEPARATOR = System.getProperty("file.separator");
    }

    /**
     * <p>
     * 重jar文件中抽取出dll文件
     * </p>
     * 
     * @param fileName
     *            ：抽取文件名，包含路径
     * @param mappedName
     *            ： dll文件名
     * @return
     */
    private static boolean extract(String fileName, String mappedName) {
        FileOutputStream os = null;
        InputStream is = null;
        File file = new File(fileName);
        try {
            // 如果文件存在则先进行删除操作
            if (file.exists()) {
                file.delete();
            }
            // 从jar文件中读取dll文件
            is = JniLibrary.class.getResourceAsStream("/resources/" + mappedName);
            if (is != null) {
                int read;
                byte[] buffer = new byte[4096];
                os = new FileOutputStream(fileName);
                while ((read = is.read(buffer)) != -1) {
                    os.write(buffer, 0, read);
                }
                os.close();
                is.close();
                return true;
            }
        } catch (Throwable e) {
            try {
                if (os != null)
                    os.close();
                if (is != null)
                    is.close();
            } catch (IOException e1) {
            }
        }
        return false;
    }

    private static boolean load(String libName) {
        try {
            if (libName.indexOf(SEPARATOR) != -1) {
                System.load(libName);
                return true;
            }
        } catch (UnsatisfiedLinkError e) {
            e.printStackTrace();
        }
        return false;
    }

    public static void extract(String name) {
        String libName = name;
        // 尝试从系统临时目录加载该文件
        String path = System.getProperty("java.io.tmpdir"); //$NON-NLS-1$
        if (path != null) {
            // 创建jni文件夹
            path = path + "jni";
            File file = new File(path);
            path = file.getAbsolutePath();
            // 文件夹是否存在
            if (!file.exists()) {
                if (!file.mkdirs()) {
                    throw new UnsatisfiedLinkError("创建文件夹" + path + "失败");
                }
            }
            String fileName = path + SEPARATOR + libName;
            file = new File(fileName);
            if (!file.exists()) {
                extract(fileName, libName);
            }
        }
    }

    /**
     * 加载类库
     * 
     * @param name: dll名称
     * @param expdate: dll最后修改日期.格式为:yyyy-MM-dd.如:2009-06-11
     */
    public static void loadLibrary(String name, String expdate) {
        String libName = name;
        // 尝试从系统临时目录加载该文件
        String path = System.getProperty("java.io.tmpdir"); //$NON-NLS-1$
        if (path != null) {
            // 创建jni文件夹
            path = path + "jni";
            File file = new File(path);
            path = file.getAbsolutePath();
            // 文件夹是否存在
            if (!file.exists()) {
                if (!file.mkdirs()) {
                    throw new UnsatisfiedLinkError("创建文件夹" + path + "失败");
                }
            }
            String fileName = path + SEPARATOR + libName;
            file = new File(fileName);
            // 判断文件是否存在，不存在进行重新生成
            Date date = new Date(file.lastModified());
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
            String modifyDate = sdf.format(date);
            if (!file.exists() || !modifyDate.equals(expdate)) {
                if (extract(fileName, libName)) {
                    load(fileName);
                    return;
                }
            }
            if (load(fileName))
                return;
        }
        // 加载失败，从临时目录和jar文件都都没有找到该文件
        throw new UnsatisfiedLinkError("no " + libName + " in java.io.tmpdir or the jar file");
    }

}