MySQL---数据库从入门走向大神系列(十二)-构建MVC项目-阿里云开发者社区

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

MySQL---数据库从入门走向大神系列(十二)-构建MVC项目