Java加载properties文件实现方式详解

package com.util;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
import java.util.PropertyResourceBundle;
import java.util.ResourceBundle;

public class PropertiesUtil {
  private static String basePath = "src/prop.properties";
  private static String name = "";
  private static String nickname = "";
  private static String password = "";

  /**
   * 一、 使用java.util.Properties类的load(InputStream in)方法加载properties文件
   *
   */
  public static String getName1() {
    try {
      Properties prop = new Properties();
      InputStream is = new FileInputStream(basePath);
      prop.load(is);
      name = prop.getProperty("username");
    } catch (FileNotFoundException e) {
      e.printStackTrace();
    } catch (IOException e) {
      e.printStackTrace();
    }
    return name;
  }

  /**
   * 二、 使用class变量的getResourceAsStream()方法
   * 注意：getResourceAsStream()读取路径是与本类的同一包下
   *
   */
  public static String getName2() {
    Properties prop = new Properties();
    InputStream is = PropertiesUtil.class
        .getResourceAsStream("/com/util/prop.properties");
    try {
      prop.load(is);
      name = prop.getProperty("username");
    } catch (IOException e) {
      e.printStackTrace();
    }
    return name;
  }

  /**
   * 三、
   * 使用class.getClassLoader()所得到的java.lang.ClassLoader的getResourceAsStream()方法
   * getResourceAsStream(name)方法的参数必须是包路径+文件名+.后缀 否则会报空指针异常
   *
   */
  public static String getName3() {
    Properties prop = new Properties();
    InputStream is = PropertiesUtil.class.getClassLoader()
        .getResourceAsStream("com/util/prop.properties");
    try {
      prop.load(is);

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

  /**
   * 四、 使用java.lang.ClassLoader类的getSystemResourceAsStream()静态方法
   * getSystemResourceAsStream()方法的参数格式也是有固定要求的
   *
   */
  public static String getName4() {
    Properties prop = new Properties();
    InputStream is = ClassLoader
        .getSystemResourceAsStream("com/util/prop.properties");
    try {
      prop.load(is);
      name = prop.getProperty("username");
    } catch (IOException e) {
      e.printStackTrace();
    }
    return name;
  }

  /**
   * 五、 使用java.util.ResourceBundle类的getBundle()方法
   * 注意：这个getBundle()方法的参数只能写成包路径+properties文件名，否则将抛异常
   *
   */
  public static String getName5() {
    ResourceBundle rb = ResourceBundle.getBundle("com/util/prop");
    password = rb.getString("password");
    return password;
  }

  /**
   * 六、 使用java.util.PropertyResourceBundle类的构造函数
   *
   */
  public static String getName6() {
    try {
      InputStream is = new FileInputStream(basePath);
      ResourceBundle rb = new PropertyResourceBundle(is);
      nickname = rb.getString("nickname");
    } catch (FileNotFoundException e) {
      e.printStackTrace();
    } catch (IOException e) {
      e.printStackTrace();
    }

    return nickname;
  }

  /**
   * 测试
   *
   */
  public static void main(String[] args) {
    System.out.println("name1:" + PropertiesUtil.getName1());
    System.out.println("name2:" + PropertiesUtil.getName2());
    System.out.println("name3:" + PropertiesUtil.getName3());
    System.out.println("name4:" + PropertiesUtil.getName4());
    System.out.println("password:" + PropertiesUtil.getName5());
    System.out.println("nickname:" + PropertiesUtil.getName6());
  }
}