java 读取本地文件实例详解

package cn.com.xinli.monitor.utils;

import org.w3c.dom.Document;
import org.w3c.dom.Element;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import java.io.File;
/**
 * Created by jiyy on 2017/4/6.
 */
public class ReadXmlTest {

  public static void main(String[] args){

    Element element = null;
    // 可以使用绝对路劲
    File f = new File("D:/workspace-idea/monitor-service/src/main/resources/logMonitor.xml");
    // documentBuilder为抽象不能直接实例化(将XML文件转换为DOM文件)
    DocumentBuilder db = null;
    DocumentBuilderFactory dbf = null;
    try {
      // 返回documentBuilderFactory对象
      dbf = DocumentBuilderFactory.newInstance();
      // 返回db对象用documentBuilderFatory对象获得返回documentBuildr对象
      db = dbf.newDocumentBuilder();
      // 得到一个DOM并返回给document对象
      Document dt = db.parse(f);
      // 得到一个elment根元素
      element = dt.getDocumentElement();
      // 获得根节点
      System.out.println("根元素：" + element.getNodeName());
    }catch (Exception e ){
      e.printStackTrace();
    }
  }

}

package cn.com.xinli.monitor.test;

import org.apache.commons.io.IOUtils;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.DocumentHelper;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URISyntaxException;

/**
 * Created by jiyy on 2017/4/6.
 */
public class ReadFileTest {

  public static void main(String[] args){


    //方法一：本地绝对路径获取xml文件内容，项目外的路径
    String fileUrl = "/D:/workspace-idea/monitor-service/src/main/resources/logMonitor.xml";
    InputStream fis = null;
    try {

      fis = new FileInputStream(new File(fileUrl));
      String content = IOUtils.toString(fis,"UTF-8");
      Document document = DocumentHelper.parseText(content);
    } catch (java.io.IOException e) {
      e.printStackTrace();
    } catch (DocumentException e) {
      e.printStackTrace();
    }

    //方法二:项目绝对路径是在本class文件所在项目的根目录下找，也就是classes/下
    try {
      String content2 = IOUtils.toString(ReadFileTest.class.getResourceAsStream("/logMonitor.xml"), "UTF-8");
      Document document2 = DocumentHelper.parseText(content2);
    } catch (IOException e) {
      e.printStackTrace();
    }catch (DocumentException e) {
      e.printStackTrace();
    }
    //方法三：相对目录，在本ReadFileTest编译后的.class文件同级目录
    try {
      String content3 = IOUtils.toString(ReadFileTest.class.getResourceAsStream("logMonitor.xml"), "UTF-8");
      Document document3 = DocumentHelper.parseText(content3);
    } catch (IOException e) {
      e.printStackTrace();
    }catch (DocumentException e) {
      e.printStackTrace();
    }
    //方法四：相对目录，在本ReadFileTest编译后的.class文件上级目录的config目录下
    try {
      String content4 = IOUtils.toString(ReadFileTest.class.getResourceAsStream("../config/logMonitor.xml"), "UTF-8");
      Document document4 = DocumentHelper.parseText(content4);
    } catch (IOException e) {
      e.printStackTrace();
    }catch (DocumentException e) {
      e.printStackTrace();
    }
    //方法五：动态获取相对目录
    try {
      String xmlPath = "logMonitor.xml";
      //获取当前类加载的根目录，如：/C:/Program Files/Apache/Tomcat 6.0/webapps/fee/WEB-INF/classes/
      String path = ReadFileTest.class.getClassLoader().getResource("").toURI().getPath();
      // 把文件读入文件输入流，存入内存中
      FileInputStream in = new FileInputStream(new File(path + xmlPath));
      String content5 = IOUtils.toString(in,"UTF-8");
      Document document5 = DocumentHelper.parseText(content5);
    } catch (IOException e) {
      e.printStackTrace();
    } catch (DocumentException e) {
      e.printStackTrace();
    }catch (URISyntaxException e) {
      e.printStackTrace();
    }
  }
}