Java安全编码:防范Java安全漏洞的最佳实践

对于Linux/Unix操作系统用户:
- 只安装Java运行时环境(JRE)，而不是开发工具包(JDK)。
- 禁用Java浏览器插件，可以使用Firefox配置插件来实现。
- 禁用Java Web Start工具，可以通过取消该特权的许可来实现。

//设置文件的权限为只读
File file = new File("test");
file.setReadOnly();
//检查文件是否存在
File file = new File("test");
if(!file.exists()){
    System.out.println("文件不存在!");
    return;
}
//检查文件是否可读
if(!file.canRead()){
    System.out.println("文件不可读!");
    return;
}
//通过FileInputStream读取文件
try {
    FileInputStream fileInputStream = new FileInputStream(file);
    //读取文件内容
    //...
    fileInputStream.close();
} catch (FileNotFoundException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
}

//加密
byte[] secretBytes = secret.getBytes("UTF-8");
//生成密钥
KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
keyGenerator.init(128);
SecretKey secretKey = keyGenerator.generateKey();
//加密
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.ENCRYPT_MODE, secretKey);
byte[] encryptedBytes = cipher.doFinal(secretBytes);
//解密
Cipher cipher = Cipher.getInstance("AES");
cipher.init(Cipher.DECRYPT_MODE, secretKey);
byte[] decryptedBytes = cipher.doFinal(encryptedBytes);
String decryptedText = new String(decryptedBytes, "UTF-8");

//创建HTTPS连接
URL url = new URL("https://www.example.com");
HttpsURLConnection httpsURLConnection = (HttpsURLConnection) url.openConnection();
//加载证书
String keyStoreFile = "client.keystore";
char[] keyStorePassword = "password".toCharArray();
KeyStore keyStore = KeyStore.getInstance("JKS");
keyStore.load(new FileInputStream(keyStoreFile), keyStorePassword);
KeyManagerFactory keyManagerFactory = KeyManagerFactory.getInstance("SunX509");
keyManagerFactory.init(keyStore, keyStorePassword);
//设置连接参数
SSLContext sslContext = SSLContext.getInstance("TLS");
sslContext.init(keyManagerFactory.getKeyManagers(), null, null);
httpsURLConnection.setSSLSocketFactory(sslContext.getSocketFactory());
httpsURLConnection.setRequestMethod("GET");
//发起连接
httpsURLConnection.connect();

public String filter(String input) {
        if (!hasSpecialCharacter(input)) {
            return input;
        }
        StringBuilder filtered = new StringBuilder(input.length());
        char prev = 0;
        for (int i = 0; i < input.length(); i++) {
            char next = input.charAt(i);
            if (next == '<' || next == '>') {
                continue;
            }
            if (next == '&' && prev == '#') {
                filtered.setCharAt(filtered.length() - 1, next);
            } else {
                filtered.append(next);
            }
            prev = next;
        }
        return filtered.toString();
    }