MySQL---数据库从入门走向大神系列(十二)-构建MVC项目

这个是对前面技术的一个小总结吧，用到的大概技术有： MVC框架，加注解，Struts框架的思想，动态代理，线程管理对象ThreadLocal，Connection对象池，Properties文件读取，EL表达式，JSTL，JavaBean，Java访问MySQL数据库，增删改查…

其实做出来界面挺简单：

完整的项目链接： https://github.com/chenhaoxiang/Java/tree/master/myMvcWeb2

这里只写出一些核心的类的代码：

Book.java:

package cn.hncu.domain; /* alter table book add constraint fk_book foreign key (studid) references stud(id); 设置studid为book的外键(fk_book)为stud的主键id */ public class Book { private Integer id; private String namem; private Double price; // ※一对多关系中的多方(外键字段): 在写JavaBean时，要包含对方(一方)的整个值对象类型的变量 private Stud stud;//设置书的主人 public Book() { super(); } public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getNamem() { return namem; } public void setNamem(String namem) { this.namem = namem; } public Double getPrice() { return price; } public void setPrice(Double price) { this.price = price; } public Stud getStud() { return stud; } public void setStud(Stud stud) { this.stud = stud; } @Override public int hashCode() { final int prime = 31; int result = 1; result = prime * result + ((id == null) ? 0 : id.hashCode()); return result; } @Override public boolean equals(Object obj) { if (this == obj) return true; if (obj == null) return false; if (getClass() != obj.getClass()) return false; Book other = (Book) obj; if (id == null) { if (other.id != null) return false; } else if (!id.equals(other.id)) return false; return true; } }

Stud.java

package cn.hncu.domain; import java.util.ArrayList; import java.util.List; public class Stud { private String id; private String name; //※一对多中的一方: 添加一个集合(用set也行)以表示该关系 private List<Book > books = new ArrayList<Book>(); public Stud() { super(); } public String getId() { return id; } public void setId(String id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public List<Book> getBooks() { return books; } public void setBooks(List<Book> books) { this.books = books; } @Override public int hashCode() { final int prime = 31; int result = 1; result = prime * result + ((id == null) ? 0 : id.hashCode()); return result; } @Override public boolean equals(Object obj) { if (this == obj) return true; if (obj == null) return false; if (getClass() != obj.getClass()) return false; Stud other = (Stud) obj; if (id == null) { if (other.id != null) return false; } else if (!id.equals(other.id)) return false; return true; } //注意,如果要添加toString()方法，注意一对多关系中的信息输出嵌套 }

TxProxy.java:

package cn.hncu.pubs.tx; import java.lang.reflect.InvocationHandler; import java.lang.reflect.Method; import java.lang.reflect.Proxy; import java.sql.Connection; import cn.hncu.pubs.ConnsUtil; public class TxProxy implements InvocationHandler{ private Object srcObj; public TxProxy(Object srcObj) { this.srcObj = srcObj; } /* 版本1 public static Object getProxy(Object srcObj){ Object proxiedObj = Proxy.newProxyInstance(TxProxy.class.getClassLoader(), srcObj.getClass().getInterfaces(), new TxProxy(srcObj)); return proxiedObj; } */ /* 版本2 public static<T> T getProxy(Object srcObj, Class<T> cls){ Object proxiedObj = Proxy.newProxyInstance(TxProxy.class.getClassLoader(), srcObj.getClass().getInterfaces(), new TxProxy(srcObj)); return (T)proxiedObj; } */ /* 版本3 public static<T> T getProxy(Class<T> cls){ Object srcObj = null; try { srcObj = cls.newInstance(); } catch (InstantiationException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } Object proxiedObj = Proxy.newProxyInstance(TxProxy.class.getClassLoader(), srcObj.getClass().getInterfaces(), new TxProxy(srcObj)); return (T)proxiedObj; } */ //版本4 public static<T> T getProxy(T srcObj){ Object proxiedObj = Proxy.newProxyInstance(TxProxy.class.getClassLoader(), srcObj.getClass().getInterfaces(), new TxProxy(srcObj)); return (T)proxiedObj; } @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { //判断method方法是不是添加了注解 if(method.isAnnotationPresent(Transaction.class)){ Connection con=null; Object returnValue =null; try { con = ConnsUtil.getConnection(); con.setAutoCommit(false); System.out.println("在动态代理中开启一个事务...."); returnValue = method.invoke(srcObj, args); con.commit(); System.out.println("在动态代理中提交一个事务...."); } catch (Exception e) { con.rollback(); System.out.println("在动态代理中回滚一个事务...."); }finally{ if(con!=null){ try { con.setAutoCommit(true); con.close(); } catch (Exception e) { throw new RuntimeException("数据库连接关闭失败", e); } } } return returnValue; }else{//没有添加注解,直接放行 return method.invoke(srcObj, args); } } }

Transaction.java:注解

package cn.hncu.pubs.tx; import java.lang.annotation.ElementType; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; @Retention(RetentionPolicy.RUNTIME) @Target(value=ElementType.METHOD) public @interface Transaction { }

BaseServlet.java:

package cn.hncu.pubs; import java.io.IOException; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * @author 陈浩翔 * * 2016-8-15 */ public abstract class BaseServlet extends HttpServlet{ @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doPost(req, resp); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { req.setCharacterEncoding("utf-8"); resp.setCharacterEncoding("utf-8"); String cmd = req.getParameter("cmd"); if(cmd==null){ cmd="execute"; } try { System.out.println("this:"+this); //下面这句不能访问私有方法 //Method m = this.getClass().getMethod(cmd, HttpServletRequest.class,HttpServletResponse.class ); //如果要用类反射实现访问类的私有方法，则需要这2步,这样子类的方法就不用设置成public了。 //1获得私有方法 Method m = this.getClass().getDeclaredMethod(cmd, HttpServletRequest.class,HttpServletResponse.class ); //2设置私有方法可以被访问 m.setAccessible(true); m.invoke(this, req,resp);//这里的this是子类对象，谁调用这里的，这个this就是谁 //下面这几句是给大家启发Struts框架的思想 // String str =(String) m.invoke(this, request,response); // String resPage = "";//从配置struts.xml文件中读取str所对应的结果页面的地址 // request.getRequestDispatcher(resPage).forward(request,response); } catch (NoSuchMethodException e) { e.printStackTrace(); } catch (SecurityException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } catch (IllegalArgumentException e) { e.printStackTrace(); } catch (InvocationTargetException e) { e.printStackTrace(); } } //如果没有参数cmd为null，转向的界面，由子类自己实现 public abstract void execute(HttpServletRequest request, HttpServletResponse response); }

ConnsUtil.java

package cn.hncu.pubs; import java.io.IOException; import java.lang.reflect.InvocationHandler; import java.lang.reflect.Method; import java.lang.reflect.Proxy; import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.util.ArrayList; import java.util.List; import java.util.Properties; public class ConnsUtil { private static List<Connection> pool = new ArrayList<Connection>(); private static final int NUM = 3; private static ThreadLocal<Connection> t = new ThreadLocal<Connection>(); static{ try { //读取配置文件 Properties p = new Properties(); p.load(ConnsUtil.class.getClassLoader().getResourceAsStream("jdbc.properties")); String driver = p.getProperty("driver"); String url = p.getProperty("url"); String user = p.getProperty("username"); String password = p.getProperty("password"); Class.forName(driver); for(int i=0;i<NUM;i++){ final Connection conn = DriverManager.getConnection(url, user, password); //System.out.println(conn.getClass().getClassLoader());//AppClassLoader //使用动态代理,代理conn对象，实现对close方法的拦截 Object obj = Proxy.newProxyInstance(ConnsUtil.class.getClassLoader(), new Class[]{Connection.class}, new InvocationHandler() { @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { //拦截close方法 if(method.getName().equalsIgnoreCase("close") &&(args==null||args.length==0) ){ pool.add((Connection)proxy); //proxy为代理后的对象 t.set(null);//把存储在本地线程管理类中的当前线程对应的对象设为空 return null; } //conn为被代理的对象 return method.invoke(conn, args); } }); pool.add( (Connection)obj);//把代理后的conn对象即obj加入池中 } } catch (IOException e) { e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } } public static synchronized Connection getConnection() throws InterruptedException{ //从本地线程管理对象t中拿 Connection con = t.get(); if(con==null){ if(pool.size()<=0){ Thread.sleep(50); return getConnection(); } con=pool.remove(0); //放入到t中 t.set(con); } return con; } }

StudServlet.java:

package cn.hncu.stud; import java.io.IOException; import java.sql.SQLException; import java.util.List; import java.util.Map; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import cn.hncu.domain.Book; import cn.hncu.domain.Stud; import cn.hncu.pubs.BaseServlet; import cn.hncu.pubs.tx.TxProxy; import cn.hncu.stud.service.IStudService; import cn.hncu.stud.service.StudService; public class StudServlet extends BaseServlet { //版本1 //private IStudService service = (IStudService) TxProxy.getProxy(new StudService()); //版本2 //private IStudService service = TxProxy.getProxy(new StudService(),IStudService.class); //版本3 //private IStudService service = TxProxy.getProxy(StudService.class);//用实现类的class //版本4 private IStudService service = TxProxy.getProxy(new StudService());//用实现类的class private void save(HttpServletRequest request, HttpServletResponse response) throws InterruptedException, ServletException, IOException { //收集并封装stud String name = request.getParameter("name"); if(name==null||name.trim().length()<=0){ response.sendRedirect("index.jsp");//重定向 return ; } Stud stud = new Stud(); stud.setName(name); //收集并封装所有book String bookNames[] = request.getParameterValues("bookname");//获取多个值 String prices[] = request.getParameterValues("price"); if(bookNames!=null){ for(int i=0;i<bookNames.length;i++){ Book book = new Book(); if(bookNames[i]==null || bookNames[i].trim().length()<=0){ continue; } book.setNamem(bookNames[i]); if(prices[i]!=null && prices[i].trim().length()!=0 ){ Double price=0.0; try { price = Double.parseDouble(prices[i]); } catch (NumberFormatException e) { price=0.0; } book.setPrice(price); } book.setStud(stud); //继续封装stud----为stud中的books属性赋值--一方中的集合 stud.getBooks().add(book); } } try { service.save(stud); } catch (SQLException e) { e.printStackTrace(); } } private void query(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { List<Map<String, String>> studs = service.query(); request.setAttribute("studs", studs); request.getRequestDispatcher("/jsps/show.jsp").forward(request, response); } @Override public void execute(HttpServletRequest request, HttpServletResponse response) { System.out.println("调用默认业务处理方法...."); } }

BookDAOJdbc.java:

package cn.hncu.stud.dao; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.SQLException; import java.util.List; import cn.hncu.domain.Book; import cn.hncu.pubs.ConnsUtil; public class BookDAOJdbc implements IBookDAO { @Override public void save(List<Book> books) throws InterruptedException, SQLException { Connection con = ConnsUtil.getConnection(); String sql = "insert into book(name,price,studid) values(?,?,?)"; PreparedStatement pst = con.prepareStatement(sql); for(Book book:books){ pst.setString(1, book.getNamem()); pst.setDouble(2, book.getPrice()); //stud中设置了uuid这里才能设置成功 pst.setString(3, book.getStud().getId()); pst.addBatch(); } pst.executeBatch(); } }

StudDAOJdbc.java

package cn.hncu.stud.dao; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.UUID; import cn.hncu.domain.Stud; import cn.hncu.pubs.ConnsUtil; public class StudDAOJdbc implements StudDAO { @Override public List<Map<String, String>> query() { List<Map<String, String>> list = new ArrayList<Map<String,String>>(); Connection con = null; try { con = ConnsUtil.getConnection(); String sql="select * from stud"; Statement st = con.createStatement(); ResultSet rs = st.executeQuery(sql); while(rs.next()){ Map<String, String> map = new HashMap<String, String>(); map.put("id", rs.getString("id")); map.put("name", rs.getString("name")); //一个map就是一条记录(数据行) list.add(map); } } catch (InterruptedException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); }finally{ if(con!=null){ try { con.close(); } catch (SQLException e) { throw new RuntimeException("数据库连接关闭失败", e); } } } return list; } @Override public void save(Stud stud) throws InterruptedException, SQLException { Connection con = ConnsUtil.getConnection(); String sql = "insert into stud values(?,?)"; PreparedStatement pst = con.prepareStatement(sql); String uuid = UUID.randomUUID().toString().replaceAll("-",""); pst.setString(1, uuid); pst.setString(2, stud.getName()); pst.executeUpdate(); //在这里为book补外键字段的值 stud.setId(uuid); //这一句执行在前，这样在BookDAOJdbc中会调用book.getStud().getId()就可以拿到该id值了 } }

IStudService.java:

package cn.hncu.stud.service; import java.sql.SQLException; import java.util.List; import java.util.Map; import cn.hncu.domain.Stud; import cn.hncu.pubs.tx.Transaction; public interface IStudService { public abstract List< Map<String, String> > query(); @Transaction//注意，注解必须加在接口上，加在实现类上是无效的!,因为我们的动态代理是面向接口的 public abstract void save(Stud stud) throws InterruptedException, SQLException; }

StudService.java:

package cn.hncu.stud.service; import java.sql.SQLException; import java.util.List; import java.util.Map; import cn.hncu.domain.Stud; import cn.hncu.stud.dao.BookDAOJdbc; import cn.hncu.stud.dao.IBookDAO; import cn.hncu.stud.dao.StudDAO; import cn.hncu.stud.dao.StudDAOJdbc; public class StudService implements IStudService { //注入 private StudDAO studDao = new StudDAOJdbc(); private IBookDAO bookDao = new BookDAOJdbc(); @Override public List<Map<String, String>> query() { return studDao.query(); } //※利用动态代理在背后帮忙实现事务功能，注意：该方法内部的异常必须抛出来给动态代理捕捉处理 @Override public void save(Stud stud) throws InterruptedException, SQLException { studDao.save(stud);//在这个内部为stud对象补id--先执行 bookDao.save(stud.getBooks());//通过book拿到stud对象，进而拿到studid,完成外键字段的赋值 } }

jdbc.properties:

##MySQL driver=com.mysql.jdbc.Driver url=jdbc:mysql://127.0.0.1:3306/hncu?useUnicode=true&characterEncoding=utf-8 username=root password=1234 ##Oracle #driver=oracle.jdbc.driver.OracleDriver #url=jdbc:oracle:thin:@localhost:1521:orcl #username=scott #password=tiger

index.jsp:

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>mvc示例演示</title> </head> <body> <br/> <a href='<c:url value="/StudServlet?cmd=query"></c:url>'>学生信息查询</a> <hr/> <form action="<c:url value='/StudServlet?cmd=save'/>" method="post"> 姓名:<input type="text" name="name" /><br/> <fieldset style="width: 200px"> <legend>图书1</legend> 书名:<input type="text" name="bookname" /><br/><br/> 价格:<input type="text" name="price" /> </fieldset> <fieldset style="width: 200px"> <legend>图书2</legend> 书名:<input type="text" name="bookname" /><br/><br/> 价格:<input type="text" name="price" /> </fieldset><br/> <input type="submit" value="保存"> </form> <br/> <a href="<c:url value='/StudServlet'/>">默认请求</a> </body> </html>

show.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>学生信息查询</title> <style type="text/css"> table,tr,td,th{ border: 1px; border-style: solid; margin: auto; } </style> </head> <body style="text-align: center;"> <h2>学生信息</h2> <table> <tr> <th>ID</th> <th>姓名</th></tr> <c:forEach items="${studs}" var="stud"> <tr> <td>${stud.id }</td> <td>${stud.name }</td> </tr> </c:forEach> </table> </body> </html>

web.xml

<servlet> <servlet-name>StudServlet</servlet-name> <servlet-class>cn.hncu.stud.StudServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>StudServlet</servlet-name> <url-pattern>/StudServlet</url-pattern> </servlet-mapping>

嗯，我就不做过多的解释啦，这个只是自己对以前知识点的一个小总结吧。

转载请附上原文博客链接： http://blog.csdn.net/qq_26525215

谙忆 认证博客专家 Java 公众号：程序编程之旅。曾经写过C、C++,使用过Cocos2dx开发过游戏、安卓端、IOS端、PC端页面均开发过。目前专注Java开发，SaaS内核、元数据的研究。偶尔玩玩爬虫