1：自定義註解進行字段隱藏（簡單版）

java 中對自定義註解的說明請參見：

http://www.cnblogs.com/peida/archive/2013/04/24/3036689.html

http://www.cnblogs.com/peida/archive/2013/04/26/3038503.html

更強大更復雜版本請看：
http://blog.csdn.net/liuc0317/article/details/48787793

下面是我自己寫的，還有部分需要完善，比如傳入類型等等。
//==============註解================
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface SensitiveInfo {

public SensitiveUtils.sensitiveType type();

}
//=============實體類====================
簡單，就使用了2個字段
public class User {

@SensitiveInfo(type = sensitiveType.str)
private String name;

private String password;
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
public String getPassword() {
    return password;
}
public void setPassword(String password) {
    this.password = password;
}
@Override
public String toString() {
    return "User [name=" + name + ", password=" + password + "]";
}

}

//==============主要方法====================
比較懶，直接使用main方法測試
public class SensitiveUtils {

public enum sensitiveType {
    str;
}

public static String str(String ss) {
    if (null == ss) {
        return "";
    }
    String s1 = ss.replaceAll("(.)", "*");
    return s1;
}

public static void main(String[] args) {
    User user = new User();
    user.setName("xiaoming");
    user.setPassword("123456");
    System.out.println(user.getName());
    System.out.println("===================");
    System.out.println(SensitiveUtils.str(user.getName()));
    System.out.println("===================");
    System.out.println(user);
}

}
//================結果測試==============

xiaoming

**

User [name=xiaoming, password=123456]