适合新手学习的Java语言 例题 【3】

23.编程实现序列化的Student（sno,sname）对象在网络上的传输
package com.softeem.demo;
 
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.net.ServerSocket;
import java.net.Socket;
 
class Student implements Serializable {
        private int sno;
        private String sname;
 
        public Student(int sno, String sname) {
               this.sno = sno;
               this.sname = sname;
        }
 
        public int getSno() {
               return sno;
        }
 
        public void setSno(int sno) {
               this.sno = sno;
        }
 
        public String getSname() {
               return sname;
        }
 
        public void setSname(String sname) {
               this.sname = sname;
        }
 
        @Override
        public String toString() {
               return "学号:" + sno + ";姓名:" + sname;
        }
 
}
 
class MyClient extends Thread {
        @Override
        public void run() {
               try {
                      Socket s = new Socket("localhost", 9999);
                      ObjectInputStream ois = new ObjectInputStream(s.getInputStream());
                      Student stu = (Student) ois.readObject();
                      System.out.println("客户端程序收到服务器端程序传输过来的学生对象>> " + stu);
                      ois.close();
                      s.close();
               } catch (IOException e) {
                      // TODO Auto-generated catch block
                      e.printStackTrace();
               } catch (ClassNotFoundException e) {
                      // TODO Auto-generated catch block
                      e.printStackTrace();
               }
        }
}
 
class MyServer extends Thread {
 
        @Override
        public void run() {
               try {
                      ServerSocket ss = new ServerSocket(9999);
                      Socket s = ss.accept();
                      ObjectOutputStream ops = new ObjectOutputStream(s.getOutputStream());
                      Student stu = new Student(1, "赵本山");
                      ops.writeObject(stu);
                      ops.close();
                      s.close();
                      ss.close();
               } catch (IOException e) {
                      // TODO Auto-generated catch block
                      e.printStackTrace();
               }
        }
 
}
 
public class TestTransfer {
        public static void main(String[] args) {
               new MyServer().start();
               new MyClient().start();
        }
}
l     JDBC
24.用dom4j组件解析如下XML格式的文件：
<?xml version="1.0" encoding="UTF-8"?>
<generator>
<table name="login" operation="1">
        <column name="username" handle="0">aaa</column>
        <column name="password" handle="0">123</column>
</table>
<table name="login" operation="2">
        <column name="id" handle="1">1</column>
        <column name="username" handle="0">bbb</column>
        <column name="password" handle="0">444</column>
</table>
<table name="login" operation="3">
        <column name="id" handle="1">4</column>
</table>
</generator>
规则：<table>operation 1表insert,2表update，3表delete.
<column>handle 1表作为where条件,0表作为操作字段。
要求：按照规则生成三条SQL语句！(即做一个方法解析xml文件生成一个含有三条SQL语句的字符串)
/**
      *解析XML文件生成一个含有可执行SQL语句的字符串
      *@paramxmlFileName
      *@returnSQL
      */
     public String parseXmltoSQL(String xmlFileName) {
        StringBuffer sbsql = new StringBuffer();
        SAXReader reader = new SAXReader();
        try {
            Document document = reader.read(new File(xmlFileName));
            Element element = document.getRootElement();
            Iterator it = element.elementIterator("table");
            while (it.hasNext()) {
               element = (Element) it.next();
               //获得对表的操作
               String oper = element.attributeValue("operation");
               //获得表名
               String tableName = element.attributeValue("name");
               if ("1".equals(oper)) {
                   sbsql.append("insert into ").append(tableName);
                   Iterator it2 = element.elementIterator("column");
                    String columnName1 = null;
                    String columnValue1 = null;
                    String columnName2 = null;
                    String columnValue2 = null;
                   if (it2.hasNext()) {
                      element = (Element) it2.next();
                       columnName1 = element.attributeValue("name");
                       columnValue1 = element.getText();
                   }
                   if (it2.hasNext()) {
                      element = (Element) it2.next();
                       columnName2 = element.attributeValue("name");
                       columnValue2 = element.getText();
                   }
                   sbsql.append("("+columnName1+","+columnName2+")"+" values('"+columnValue1+"','"+columnValue2+"')\n");
                   
               } elseif ("2".equals(oper)) {
                   sbsql.append("update ").append(tableName);
                   Iterator it2 = element.elementIterator("column");
                    String columnName1 = null;
                    String columnValue1 = null;
                    String columnName2 = null;
                    String columnValue2 = null;
                    String columnName3 = null;
                    String columnValue3 = null;
                    if (it2.hasNext()) {
                          element = (Element) it2.next();
                           columnName1 = element.attributeValue("name");
                           columnValue1 = element.getText();
                      }
                   if (it2.hasNext()) {
                      element = (Element) it2.next();
                       columnName2 = element.attributeValue("name");
                       columnValue2 = element.getText();
                   }
                   if (it2.hasNext()) {
                      element = (Element) it2.next();
                       columnName3 = element.attributeValue("name");
                       columnValue3 = element.getText();
                   }
                   sbsql.append(" set "+columnName2+"='"+columnValue2+"',"+columnName3+"='"+columnValue3+"' where "+columnName1+"="+columnValue1+"\n");
                   
               }elseif ("3".equals(oper)) {
                   sbsql.append("delete from ").append(tableName);
                   Iterator it2 = element.elementIterator("column");
                    String columnName1 = null;
                    String columnValue1 = null;
                    if (it2.hasNext()) {
                          element = (Element) it2.next();
                           columnName1 = element.attributeValue("name");
                           columnValue1 = element.getText();
                      }
                   sbsql.append(" where "+columnName1+"="+columnValue1);
                   
               }
            }
        } catch (DocumentException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return sbsql.toString();
     }
l     JSP/SERVLET
25．写出JSP的内置对象并说明他们的作用 
request:request表示HttpServletRequest对象。它包含了有关浏览器请求的信息，并且提供了几个用于获取cookie, header数据的有用的方法。 response:response表示HttpServletResponse对象，并提供了几个用于设置送回 浏览器的响应的方法（如cookies,头信息等） out:out对象是javax.jsp.JspWriter的一个实例，并提供了几个方法使你能用于向浏览器回送输出结果。 pageContext:pageContext表示一个javax.servlet.jsp.PageContext对象。它是用于方便存取各种范围的名字空间、servlet相关的对象的API，并且包装了通用的servlet相关功能的方法。 session:session表示一个请求的javax.servlet.http.HttpSession对象。Session可以存贮用户的状态信息 application:applicaton 表示一个javax.servle.ServletContext对象。这有助于查找有关servlet引擎和servlet环境的信息 config:config表示一个javax.servlet.ServletConfig对象。该对象用于存取servlet实例的初始化参数。 page:page表示从该页面产生的一个servlet实例。
exception: exception对象是一个例外对象，当一个页面在运行过程中发生了例外，就产生这个对象。如果一个JSP页面要应用此对象，就必须把isErrorPage设为true，否则无法编译。他实际上是java.lang.Throwable的对象