Tomcat parses XML and creates objects through reflection

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.List;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;
public class ServerReadXML1 {
  public static void main(String[] args)
      throws DocumentException, ClassNotFoundException, InstantiationException, IllegalAccessException,
      NoSuchMethodException, SecurityException, IllegalArgumentException, InvocationTargetException {
    // Now if you enter a Servlet url-pattern in the browser
    String urlPattern = "/first";
    // Get the class name according to urlPattern String className = getClassByUrl(urlPattern);
    // Get the Class object based on the full class name Class clazz = Class.forName(className);
    // Create the specified object by reflecting the clazz object Object obj = clazz.newInstance();
    // Get the service method Method method = clazz.getDeclaredMethod("service");
    // Get permissions method.setAccessible(true);
    // Execute the service method method.invoke(obj);
  }
  private static String getClassByUrl(String urlPattern) throws DocumentException {
    // 1. Create a SAXReader object SAXReader reader = new SAXReader();
    // 2. Read the file Document document = reader.read(ServerReadXML1.class.getClassLoader().getResourceAsStream("web.xml"));
    // 3. Get the root node Element rootElement = document.getRootElement();
    //System.out.println(rootElement.getName());
    // 4. Get the child nodes List<Element> under the root node servletList = rootElement.elements();
    // Record the content of the servlet-name tag that is the same as urlPattern String servletName = "";
    // Record the content of servlet-class in the servlet tag // The content of servletClassName is the full class name of the Servlet String servletClassName = "";
    // 5. Traverse child nodes for (Element servletElement : servletList) {
      //System.out.println(servletElement.getName());
      // If it is a servlet-mapping tag, execute the code if ("servlet-mapping".equals(servletElement.getName())) {
        // Get the url-pattern tag object Element url = servletElement.element("url-pattern");
        // Check if the content of the tag is the same as the entered urlPattern value if (urlPattern.equals(url.getText())) {
          //Record the content of the servlet-name tag that is the same as urlPattern //If they are the same, record ServletName
          // Get the content of servelt-name in servlet-mapping servletName = servletElement.element("servlet-name").getText();
        }
      }
    }
    // Traverse again for (Element servletElement : servletList) {
      // If it is a servlet tag, execute this code if ("servlet".equals(servletElement.getName())) {
        // Determine whether the value of servletName obtained in the previous traversal is the same as the content of servlet-name in this traversal if (servletName.equals(servletElement.element("servlet-name").getText())) {
          // If the same record servletClassName
          servletClassName = servletElement.element("servlet-class").getText();
        }
      }
    }
    // Return the full class name of the Servlet servletClassName
    return servletClassName;
  }
}

@Test
  public void test1() throws ClassNotFoundException {
    //1. Class name.class
    Class clazz = String.class;
    System.out.println(clazz);
    //2. Object.getClass()
    Class clazz1 = "abc".getClass();
    System.out.println(clazz1);
    //3.Class.forName();
    Class clazz2 = Class.forName("java.lang.String");
    System.out.println(clazz2);
    //4.ClassLoader .loadClass("full class name")
    Class clazz3 = ReflectTest1.class.getClassLoader().loadClass("java.lang.String");
    System.out.println(clazz3);
  }

@Test
  public void test2() throws ClassNotFoundException, NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException {
    //Get the Class object to get its internal properties Class clazz = Class.forName("com.atguigu.bean.User");
    User user = new User();
    //The Field object represents the class attribute getField can only get the public attribute Field field = clazz.getField("email");
    System.out.println(field);
     //This method destroys the encapsulation of the code and is not recommended. Field field2 = clazz.getDeclaredField("id");
    System.out.println(field2);
    field2.setAccessible(true);
    field2.setInt(user, 1001);
    System.out.println(user);
  }

@Test
  public void test3() throws ClassNotFoundException, InstantiationException, IllegalAccessException, NoSuchMethodException, SecurityException, IllegalArgumentException, InvocationTargetException {
    Class clazz = Class.forName("com.atguigu.bean.User");
    //Create an object through reflection Object obj = clazz.newInstance();
    //Now we want to set the name value String fileName = "name";
    //Create a method name String methodName = "set" + fileName.substring(0, 1).toUpperCase() //N
    + fileName.substring(1).toLowerCase(); //ame
    //Get the public method according to the method name Method method = clazz.getMethod(methodName, String.class);
    //Execute the specified method method.invoke(obj, "yangjian");
    System.out.println(obj);
  }