What is a configuration file in Java

What is a configuration file in Java

Configuration file names in Java generally end with ".properties" and ".xml" , the structure of these configuration files is the same as Java's HashMap structure. Its function is to change the parameters in the code by modifying the configuration file, thereby achieving flexible parameter changes.

properties usage

driver=com.mysql.jdbc.Driver 
jdbcUrl=jdbc:mysql://localhost:3306/user 
user=root 
password=123456

/**
     * 读取config.properties文件中的内容，放到Properties类中
     * @param filePath 文件路径
     * @param key 配置文件中的key
     * @return 返回key对应的value
     */
    public static String readConfigFiles(String filePath,String key) {
        Properties prop = new Properties();
        try{
            InputStream inputStream = new FileInputStream(filePath);
            prop.load(inputStream);
            inputStream.close();
            return prop.getProperty(key);
        }catch (Exception e) {
            e.printStackTrace();
            System.out.println("未找到相关配置文件");
            return null;
        }
    }

xml usage

<?xml version="1.0" encoding="utf-8" ?>
<class>
    <student>
        <firstname>cxx1</firstname>
        <lastname>Bob1</lastname>
        <nickname>stars1</nickname>
        <marks>85</marks>
    </student>
    <student rollno="493">
        <firstname>cxx2</firstname>
        <lastname>Bob2</lastname>
        <nickname>stars2</nickname>
        <marks>85</marks>
    </student>
    <student rollno="593">
        <firstname>cxx3</firstname>
        <lastname>Bob3</lastname>
        <nickname>stars3</nickname>
        <marks>85</marks>
    </student>
</class>

package com.cxx.xml;

import org.w3c.dom.*;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
/**
 * @Author: cxx
 * Dom操作xml
 * @Date: 2018/5/29 20:19
 */
public class DomDemo {
    //用Element方式
    public static void element(NodeList list){
        for (int i = 0; i <list.getLength() ; i++) {
            Element element = (Element) list.item(i);
            NodeList childNodes = element.getChildNodes();
            for (int j = 0; j <childNodes.getLength() ; j++) {
                if (childNodes.item(j).getNodeType()==Node.ELEMENT_NODE) {
                    //获取节点
                    System.out.print(childNodes.item(j).getNodeName() + ":");
                    //获取节点值
                    System.out.println(childNodes.item(j).getFirstChild().getNodeValue());
                }
            }
        }
    }

    public static void node(NodeList list){
        for (int i = 0; i <list.getLength() ; i++) {
            Node node = list.item(i);
            NodeList childNodes = node.getChildNodes();
            for (int j = 0; j <childNodes.getLength() ; j++) {
                if (childNodes.item(j).getNodeType()==Node.ELEMENT_NODE) {
                    System.out.print(childNodes.item(j).getNodeName() + ":");
                    System.out.println(childNodes.item(j).getFirstChild().getNodeValue());
                }
            }
        }
    }

    public static void main(String[] args) {
        //1.创建DocumentBuilderFactory对象
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        //2.创建DocumentBuilder对象
        try {
            DocumentBuilder builder = factory.newDocumentBuilder();
            Document d = builder.parse("src/main/resources/demo.xml");
            NodeList sList = d.getElementsByTagName("student");
            //element(sList);
            node(sList);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Recommended tutorial:《JavaTutorial》

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