MySQL---数据库从入门走向大神系列(十二)-构建MVC项目（1）-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....");
    }
}

MySQL---数据库从入门走向大神系列(十二)-构建MVC项目（1）

Book.java:

Stud.java

TxProxy.java:

Transaction.java:注解

BaseServlet.java:

ConnsUtil.java

StudServlet.java:

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