XML parsing

One , stay java Three configuration locations and reading methods of configuration files in

（1） Same bag

InputStream in = Demo3.class.getResourceAsStream("config.xml");

（2） The root path

InputStream in = Demo1.class.getResourceAsStream("/db.properties");

（3）WIN-INF Safe path

InputStream in = Demo1.class.getResourceAsStream("/WBE-INF/db.properties");

 

  Provides a set of methods to get or close database objects

< The code is as follows >

package com.zsm.xml;
 
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
 
 
public class DBHelper {
    private static String driver;
    private static String url;
    private static String user;
    private static String password;
 
    static {//  The static method executes once    Load the driver once 
        try {
            InputStream is = DBHelper.class
                    .getResourceAsStream("config.properties");
 
            Properties properties = new Properties();
            properties.load(is);
 
            driver = properties.getProperty("driver");
            url = properties.getProperty("url");
            user = properties.getProperty("user");
            password = properties.getProperty("pwd");
 
            Class.forName(driver);
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }
    }
 
    /**
     *  Create connection 
     * 
     * @return  Connect 
     */
    public static Connection getConnection() {
        try {
            Connection conn = DriverManager.getConnection(url, user, password);
            return conn;
        } catch (SQLException e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }
    }
 
    public static void close(ResultSet rs) {
        if (null != rs) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
                throw new RuntimeException(e);
            }
        }
    }
 
    public static void close(Statement stmt) {
        if (null != stmt) {
            try {
                stmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
                throw new RuntimeException(e);
            }
        }
    }
 
    public static void close(Connection conn) {
        if (null != conn) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
                throw new RuntimeException(e);
            }
        }
    }
 
    public static void close(Connection conn, Statement stmt, ResultSet rs) {
        close(rs);
        close(stmt);
        close(conn);
    }
 
    public static boolean isOracle() {
        return "oracle.jdbc.driver.OracleDriver".equals(driver);
    }
 
    public static boolean isSQLServer() {
        return "com.microsoft.sqlserver.jdbc.SQLServerDriver".equals(driver);
    }
    
    public static boolean isMysql() {
        return "com.mysql.jdbc.Driver".equals(driver);
    }
 
    public static void main(String[] args) {
        Connection conn = DBHelper.getConnection();
        DBHelper.close(conn);
        System.out.println("isOracle;" + isOracle());
        System.out.println("isSQLServer;" + isSQLServer());
        System.out.println("isMysql;" + isMysql());
        System.out.println(" Database connection （ close ） success ");
    }
}

  ① What are the benefits of configuration files ？
 .properties/  .xml/  .yml
  (1) Make the code more flexible
  (2) Higher maintainability
  
  ② What about the location of each place
  At the same level ： Convenient for synchronous coding
  root directory ： Usually do not make frequent changes

  Why put it in web-inf Next ？

  because web-inf It belongs to the security directory （ safer ）, No direct access to , It must be accessed indirectly through the program

  If you visit directly from the page , Will give an exception

 

 
Two ,dom4j Use

（1）selectNodes

（2）selectSingleNode

（3）attributValue

（4）getText

Method 1

《 The code is as follows 》

package com.zsm.xml;
 
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
 
/**
 *  Read files in various locations 
 * @author DXY
 *2022 year 6 month 13 On the afternoon of Sunday 10:14:23
 */
public class Demo1 {
 
    /**
     *  Method 1 
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception {
        // Compatriot 
        InputStream in = Demo1.class.getResourceAsStream("db.properties");
        // root directory 
        //InputStream in = Demo1.class.getResourceAsStream("/db.properties");
        //.proerties There is a special class 
        Properties p = new Properties();
        // here p Just load db.properties All information in 
        p.load(in);
        System.out.println(p.getProperty("uname"));
        System.out.println(p.getProperty("upwd"));
    }
}

Method 2  

package com.zsm.xml;
 
import java.io.InputStream;
import java.util.List;
 
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
 
public class Demo2 {
 
    
    /**
     *  Method 2 
     * @param args
     * @throws Exception
     */
    public static void main(String[] args) throws Exception {
        // Same bag 
        InputStream in = Demo2.class.getResourceAsStream("students.xml");
        SAXReader sr = new SAXReader();
//        // Get all the contents in the configuration file to 
        Document doc = sr.read(in);
//        System.out.println(doc.asXML());
//        //selectNodes    Return the set according to the tag 
        // Get child nodes 
//        List<Element> studentEle = doc.selectNodes("students");
        // Print length 
//        System.out.println(studentEle.size());
        // obtain students Child nodes under 
//        List<Element> studentEles = studentEle.get(0).selectNodes("student");
        // Print the length of the word node 
//        System.out.println(studentEles.size());
        
        
        
        //selectNodes  By tag name . Returns a single label    It is usually used to know that the tag value appears once 
        Element studentEle = (Element) doc.selectSingleNode("students");
        // Get child nodes 
        List<Element> stuEles = studentEle.selectNodes("student");
        for (Element stuEle : stuEles) {
            //attributeValue Get the attribute value 
            System.out.println(stuEle.attributeValue("sid"));
            //getText Get the contents of the label 
            System.out.println(stuEle.selectSingleNode("name").getText());
            
        }
    }
}

< design sketch >

 

3、 ... and ,xpath Use

（1） grammar

/  Location attribute      @    attribute

（2） Case study

browser Xpath Use

lookup soo2 Student name of

《 Code demonstration 》

Method 3 and method 4

package com.zsm.xml;
 
import java.io.InputStream;
import java.util.List;
 
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.io.SAXReader;
 
public class Demo3 {
public static void main(String[] args) throws Exception {
    //   / Representative hierarchy , For finding  
    //     @ Precise positioning 
    
    /**
     *  Method 3 
     */
    InputStream in = Demo3.class.getResourceAsStream("students.xml");
    SAXReader sr = new SAXReader();
    Document doc = sr.read(in);
//    Element stus002 = (Element) doc.selectSingleNode("/students/student[@sid='s002']/name");
//    System.out.println(stus002.getText());
    
    
    /**
     *  Method four 
     */
    Element studentEle = (Element) doc.selectSingleNode("students");
    List<Element> stuEles = studentEle.selectNodes("student");
    for (Element stuEle : stuEles) {
        if("s002".equals(stuEle.attributeValue("sid"))) {
            System.out.println(stuEle.selectSingleNode("name").getText());
        }
    }
    
}
}

 

《 design sketch 》

The effect is the code of method 4

 

Four , Case study
《 Reference code 》

The cases are based on the following code blocks

<?xml version="1.0" encoding="UTF-8"?>
    <!--
        config label : Can contain 0~N individual action label 
    -->
<config>
    <!--
        action label : Can be full of 0~N individual forward label 
        path: With / Starting string , And the value must be unique   Non empty 
        type: character string , Non empty 
    -->
    <action path="/regAction" type="test.RegAction">
        <!--
            forward label : No sub tags ; 
            name: character string , same action Label under forward label name The value can't be the same  ;
            path: With / Starting string 
            redirect: Can only be false|true, Allow space , The default value is false
        -->
        <forward name="failed" path="/reg.jsp" redirect="false" />
        <forward name="success" path="/login.jsp" redirect="true" />
    </action>
 
    <action path="/loginAction" type="test.LoginAction">
        <forward name="failed" path="/login.jsp" redirect="false" />
        <forward name="success" path="/main.jsp" redirect="true" />
    </action>
</config>

（ Case study 1）

package com.zsm.xml;
 
import java.io.InputStream;
import java.util.List;
 
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
/**
 *  requirement ： Get all action Medium type value 
 * @author DXY
 *2022 year 6 month 13 On the afternoon of Sunday 11:42:12
 */
public class action01 {
    public static void main(String[] args) throws Exception {
        InputStream in = Demo3.class.getResourceAsStream("config.xml");
        SAXReader sr = new SAXReader();
        Document doc = sr.read(in);
        Element type = (Element) doc.selectSingleNode("config");
        List<Element> action = type.selectNodes("action");
        for (Element actions : action) {
                System.out.println(actions.attributeValue("type"));
        }
 
    }
}

《 design sketch 》

 

（ Case 2 ）

package com.zsm.xml;
 
import java.io.InputStream;
import java.util.List;
 
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
/**
 *  requirement ： Get the second action Of type value 
 * @author DXY
 *2022 year 6 month 13 On the afternoon of Sunday 11:42:12
 */
public class action2 {
    public static void main(String[] args) throws Exception {
        InputStream in = Demo3.class.getResourceAsStream("config.xml");
        SAXReader sr = new SAXReader();
        Document doc = sr.read(in);
        Element type2 = (Element) doc.selectSingleNode("/config/action[@path='/loginAction']");
        System.out.println(type2.attributeValue("type"));
 
    }
}

《 design sketch 》

 

（ Case three ）

package com.zsm.xml;
 
import java.io.InputStream;
import java.util.List;
 
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
/**
 *  requirement ： Get the second action All of forward Of path
 * @author DXY
 *2022 year 6 month 13 On the afternoon of Sunday 11:42:12
 */
public class action3 {
    public static void main(String[] args) throws Exception {
        InputStream in = Demo3.class.getResourceAsStream("config.xml");
        SAXReader sr = new SAXReader();
        Document doc = sr.read(in);
        //Element type2 = (Element) doc.selectSingleNode("/config/action[@path='/loginAction']/forward");
        //System.out.println(type2.attributeValue("path"));
        Element forward = (Element) doc.selectSingleNode("config/action[@path='/loginAction']");
        List<Element> path = forward.selectNodes("forward");
        for (Element paths : path) {
                System.out.println(paths.attributeValue("path"));
        }
 
    }
}

《 design sketch 》

 

（ Case four ）

package com.zsm.xml;
 
import java.io.InputStream;
import java.util.List;
 
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
/**
 *  requirement ： Get the second action The second forward Of path
 * @author DXY
 *2022 year 6 month 13 On the afternoon of Sunday 11:42:12
 */
public class action4 {
    public static void main(String[] args) throws Exception {
        InputStream in = Demo3.class.getResourceAsStream("config.xml");
        SAXReader sr = new SAXReader();
        Document doc = sr.read(in);
        //Element type2 = (Element) doc.selectSingleNode("/config/action[@path='/loginAction']/forward");
        //System.out.println(type2.attributeValue("path"));
        Element forward = (Element) doc.selectSingleNode("config/action[@path='/loginAction']");
        List<Element> path = forward.selectNodes("forward[@name='success']");
        for (Element paths : path) {
                System.out.println(paths.attributeValue("path"));
        }
 
    }
}

 《 design sketch 》