The student information in this example adds transactions to the database (the transaction can be submitted, transactions can be rolled back, and improved with local threads)
Main page index.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %><html> <head> <title>Student Information Management</title> </head> <body> <a href='<c:url value="/query"/>?cmd=query'>View student information</a> <br><br> <!-- <a href="<c:url value='/StudServlet?cmd=save' />">Student Information Add</a> --> <h2>Student Information Add</h2> <form action='<c:url value="/query"/>?cmd=add' method="post"> Name:<input type="text" name="name"/><br><br> <fieldset style="border: solid;border-color: red;width: 250px;"> <legend>Book1</legend> Title:<input type="text" name="book"/><br><br> Price:<input type="text" name="price"/> </fieldset> <br> <fieldset style="border: solid;border-color:green;width: 250px;"> <legend>Book 2</legend> Title:<input type="text" name="book"/><br><br> Price:<input type="text" name="price"/> </fieldset> <br><br> <input type="submit" value="submit"/><br><br> </form> </body></html>
Toolkit
Tool for getting database connection ConnUtils5.java
package cn.hncu.utils;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.util.ArrayList;import java.util.List;import java.util.Properties;public class ConnUtils5 { //Local thread management object, used to implement: The connection obtained by the same thread is the same private static ThreadLocal<Connection> t=new ThreadLocal<Connection>(); private final static List<Connection> pool=new ArrayList<Connection>(); private static int SIZE;//Read private ConnUtils5(){ } static{ Properties p=new Properties(); try { //The following method can read the resource file under classpath in a pure Java project, but the JavaEE project cannot be read. Because Tomcat changed the system's default class loader //p.load( ClassLoader.getSystemClassLoader().getSystemResourceAsStream("jdbc.properties")); // p.load(ClassLoader.getSystemResourceAsStream("jdbc.properties")); // Read the resource file under the classpath of the web project, use this to p.load(ConnUtils3.class.getClassLoader().getResourceAsStream("jdbc.properties")); String driver=p.getProperty("driver"); String url=p.getProperty("url"); String name=p.getProperty("username"); String pwd=p.getProperty("password"); String ssize=p.getProperty("size"); SIZE=Integer.parseInt(ssize); Class.forName(driver); for(int i=0;i<SIZE;i++){ final Connection con=DriverManager.getConnection(url,name,pwd); System.out.println("con=="+con); //Change the conn.close() method//Use proxy mode to generate an enhanced version of the conn object, intercept and change its close() method to Object nCon=Proxy.newProxyInstance( ConnUtils3.class.getClassLoader(), // conn.getClass().getInterfaces(), // This method does not work, it should be that the implementation class in the driver is not in the same space as our current program (the class loader is different) new Class[]{Connection.class}, new InvocationHandler() { @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { if(method.getName().equals("close")){ System.out.println("Return a link: "+(Connection)proxy); pool.add((Connection)proxy); return null; } return method.invoke(con, args); } }); pool.add((Connection)nCon); } } catch (Exception e) { e.printStackTrace(); } } public static synchronized Connection getConnection(){ //Get from t first, if there is one, take it out. If not, grab it in the pool and put the object in t Connection con=t.get(); if(con==null){ if(pool.size()<=0){ System.out.println("The connection in the pool is gone..."); try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } return getConnection(); } con=pool.remove(0); t.set(con);//Put it in t} return con;//Get one to move one}}acting
package cn.hncu.utils;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import java.lang.reflect.Proxy;import java.sql.Connection;import java.sql.SQLException;public class TxProxy implements InvocationHandler { private Object srcObj=null; private TxProxy(Object srcObj) { this.srcObj = srcObj; } public static Object getProxy(Object srcObj){ System.out.println("srcObj:"+srcObj); Object newObj=Proxy.newProxyInstance( TxProxy.class.getClassLoader(), srcObj.getClass().getInterfaces(), new TxProxy(srcObj)); System.out.println("newObj:"+newObj); return newObj; } @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { Connection con=null; Object returnObj=null; try { con=ConnUtils5.getConnection(); System.out.println("invoke got a link: "+con); con.setAutoCommit(false); returnObj=method.invoke(srcObj, args); System.out.println("Submit a transaction..."); con.commit(); } catch (Exception e) { try { System.out.println("Rolling back a transaction..."); con.rollback(); } catch (SQLException e1) { e1.printStackTrace(); } } finally{ try { con.setAutoCommit(true); con.close(); } catch (SQLException e) { e.printStackTrace(); } } return returnObj; }}Agent 2: No need to force transfer, but all
package cn.hncu.utils;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import java.lang.reflect.Proxy;import java.sql.Connection;import java.sql.SQLException;public class TxProxy2 implements InvocationHandler { private Object srcObj=null; private TxProxy2(Object srcObj) { this.srcObj = srcObj; } public static<T> T getProxy(Class<T> c){ Object obj=null; try { obj = c.newInstance(); } catch (Exception e) { e.printStackTrace(); } Object newObj=Proxy.newProxyInstance( TxProxy2.class.getClassLoader(), c.getInterfaces(), new TxProxy2(obj)); return (T) newObj; } @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { Connection con=null; Object returnObj=null; try { con=ConnUtils5.getConnection(); System.out.println("invoke got a link: "+con); con.setAutoCommit(false); returnObj=method.invoke(srcObj, args); System.out.println("Submit a transaction..."); con.commit(); } catch (Exception e) { try { System.out.println("Rolle back a transaction..."); con.rollback(); } catch (SQLException e1) { e1.printStackTrace(); } } finally{ try { con.setAutoCommit(true); con.close(); } catch (SQLException e) { e.printStackTrace(); } } return returnObj; }}annotation
package cn.hncu.utils;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;@Target(value=ElementType.METHOD)@Retention(RetentionPolicy.RUNTIME)public @interface Transaction {}Agent 3: Use annotations to implement transactions when needed
package cn.hncu.utils;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import java.lang.reflect.Proxy;import java.sql.Connection;import java.sql.SQLException;public class TxProxy3 implements InvocationHandler { private Object srcObj=null; private TxProxy3(Object srcObj) { this.srcObj = srcObj; } public static<T> T getProxy(T srcObj){ Object newObj=Proxy.newProxyInstance( TxProxy3.class.getClassLoader(), srcObj.getClass().getInterfaces(), new TxProxy3(srcObj)); return (T) newObj; } @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { /* This way to implement only intercepting the specified method if(method.getName().equals("close")){ ...intercept}else{ return method.invoke(srcObj, args); } */ if(method.isAnnotationPresent(Transaction.class)){ Connection con=null; Object returnObj=null; try { con=ConnUtils5.getConnection(); System.out.println("invoke got a link: "+con); con.setAutoCommit(false); //Real business code, release returnObj=method.invoke(srcObj, args); System.out.println("Submit a transaction..."); con.commit(); } catch (Exception e) { try { System.out.println("Rolle back a transaction..."); con.rollback(); } catch (SQLException e1) { e1.printStackTrace(); } } finally{ try { con.setAutoCommit(true); con.close(); } catch (SQLException e) { e.printStackTrace(); } } return returnObj; }else{ System.out.println("There is no transaction annotation, just release it!"); return method.invoke(srcObj, args); } }}Resource file jdbc.properties
##MySQLdriver=com.mysql.jdbc.Driverurl=jdbc:mysql://127.0.0.1:3306/hncu?useUnicode=true&characterEncoding=utf-8username=rootpassword=1234size=3##Oracle#driver=oracle.jdbc.driver.OracleDriver#url=jdbc:oracle:thin:@127.0.0.1:1521:orcl#username=scott#password=tiger
QueryServlet.java servlet layer of stud layer
package cn.hncu.stud.servlet;import java.io.IOException;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.stud.service.IStudService;import cn.hncu.stud.service.StudServiceImpl;import cn.hncu.utils.TxProxy3;public class QueryServlet extends HttpServlet { //Inject//1.// IStudService service=(IStudService) TxProxy.getProxy(new StudServiceImpl()); //2.// IStudService service=TxProxy2.getProxy(StudServiceImpl.class); //3. IStudService service=TxProxy3.getProxy(new StudServiceImpl()); public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doPost(request, response); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String cmd=request.getParameter("cmd"); System.out.println("cmd:"+cmd); if("query".equals(cmd)){ query(request, response); }else if("add".equals(cmd)){ add(request, response); } } public void query(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("service:"+service); List<Map<String, String>> studs=service.query(); request.setAttribute("studs", studs); request.getRequestDispatcher("/jsps/show.jsp").forward(request, response); } public void add(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //1 Collect parameters 2 Organize parameters (leave the id field in dao to supplement) String name[]=request.getParameterValues("name"); Stud s=new Stud(); s.setName(name[0]); //Book information String books[]=request.getParameterValues("book"); //Protect ---Price protection should also be written. We are lazy here if(books==null||books.length<=0){ return; } String prices[]=request.getParameterValues("price"); for(int i=0;i<books.length;i++){ Book b=new Book(); b.setName(books[i]); b.setPrice(Double.parseDouble(prices[i])); //※ Complete the data encapsulation of the "one-to-many" relationship between two value objects s.getBooks().add(b);//One-party b.setS(s);//Multiple-party} //3 Call the service layer try { service.save(s); } catch (Exception e) { //Direction failed page} }} The service layer of the stud layer
interface:
package cn.hncu.stud.service;import java.util.List;import java.util.Map;import cn.hncu.domain.Stud;import cn.hncu.utils.Transaction;public interface IStudService { public List<Map<String, String>> query(); //Note that annotations are only useful in place in the interface,,,,The method written in the implementation class is invalid (it will not decide to start the transaction) @Transaction public void save(Stud stud) throws Exception ;}Implementation Class
package cn.hncu.stud.service;import java.sql.Connection;import java.sql.SQLException;import java.util.List;import java.util.Map;import cn.hncu.domain.Stud;import cn.hncu.stud.dao.BookDAO;import cn.hncu.stud.dao.BookDAO;import cn.hncu.stud.dao.BookJdbcDao;import cn.hncu.stud.dao.StudDAO;import cn.hncu.utils.ConnUtils5;/*We usually use a table to operate independently during future development. If there are several entity tables in the system, write a few dao. * In the future, the framework will do this, and we must do this, because the architecture is good! * * In case of using transactions: * 1. If there is only one dao, but multiple SQL statements need to be executed and add, delete and modify, the transaction must be opened. 2. If a service calls multiple dao, the transaction must also be opened. */public class StudServiceImpl implements IStudService { //Inject StudDAO dao_stud=new StudJdbcDAO(); BookDAO dao_book=new BookJdbcDao(); @Override public List<Map<String, String>> query() { return dao_stud.query(); } @Override public void save(Stud stud) throws Exception { dao_stud.save(stud); dao_book.save(stud.getBooks()); }} The dao layer of the stu layer
Stud interface separation practice, one table corresponds to one dao, prepare for the framework
package cn.hncu.stud.dao;import java.util.List;import java.util.Map;import cn.hncu.domain.Stud;public interface StudDAO { public List<Map<String, String>> query(); public void save(Stud stud) throws Exception;}Stud implementation class
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.Book;import cn.hncu.domain.Stud;import cn.hncu.utils.ConnUtils3;public class StudJdbcDAO implements StudDAO { @Override public List<Map<String, String>> query() { List<Map<String, String>> list=new ArrayList<Map<String, String>>(); //A map is a row of data, List<Map> is the entire data table Connection con=null; try { con=ConnUtils3.getConnection(); Statement st=con.createStatement(); String sql="select * from stud"; ResultSet rs=st.executeQuery(sql); while(rs.next()){ Map<String,String> m=new HashMap<String, String>(); m.put("id", (String) rs.getObject(1)); m.put("name", (String) rs.getObject(2)); list.add(m); } rs.close(); st.close(); } catch (SQLException e) { e.printStackTrace(); } finally{ try { con.close(); } catch (SQLException e) { e.printStackTrace(); } } return list; } @Override public void save(Stud stud) throws Exception { Connection con=ConnUtils3.getConnection(); System.out.println("Get a link: "+con); String sql="insert into stud values(?,?)"; String uuid=UUID.randomUUID().toString().replace("-", ""); PreparedStatement pst=con.prepareStatement(sql); stud.setId(uuid);//In order to "multiple parties", that is, the book can get the "one party" id, it is specially supplemented with pst.setString(1, uuid); pst.setString(2, stud.getName()); System.out.println("1:"+uuid+",2:"+stud.getName()); pst.executeUpdate();// con.close();// get the same con, there is no need to close it here}}Book interface
package cn.hncu.stud.dao;import java.util.List;import cn.hncu.domain.Book;public interface BookDAO { public void save(List<Book> books) throws Exception;}Book implementation class
package cn.hncu.stud.dao;import java.sql.Connection;import java.sql.PreparedStatement;import java.util.List;import cn.hncu.domain.Book;import cn.hncu.utils.ConnUtils3;public class BookJdbcDao implements BookDAO { @Override public void save(List<Book> books) throws Exception { Connection con=ConnUtils3.getConnection(); System.out.println("Get a link: "+con); String sql="insert into book(name,price,studid) values(?,?,?)"; PreparedStatement pst=con.prepareStatement(sql); for(Book b:books){ pst.setString(1, b.getName()); pst.setDouble(2, b.getPrice()); pst.setObject(3, "12132312");//Exception (deliberately give a non-existent foreign key field to test transaction rollback)-test transaction rollback// pst.setObject(3, b.getS().getId()); System.out.println("1:"+b.getName()+",2:"+b.getPrice()+",3:"+b.getS().getId()); pst.addBatch();//Add to batch} pst.executeBatch();//Execute batch// con.close();//Get the same con here, no need to close here}} Value Object
Stud Object
package cn.hncu.domain;import java.util.ArrayList;import java.util.List;/* * Method for creating a "one" square value object in one-to-many*/public class Stud { private String id; private String name; //※Add a collection specifically for "multi" squares---reflecting the "one-to-many relationship" in a multi-table private List<Book> books=new ArrayList<Book>();//Note that the collection must be new at or before construction. 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 String toString() { return "id=" + id + "," + name + "," + books; }}Book object
package cn.hncu.domain;/* * Method for creating "multi" square value objects in one-to-many*/public class Book { private Integer id; // All basic data types are declared by the packaging class to prepare for future use of frameworks---the packaging class is compatible with frameworks (because generally frameworks use class reflection) private String name; private Double price; //※Add a variable of object type specifically for "one" square (note, don't use studyd)---reflect the "one-to-many relationship" in multiple tables private Stud s;//Set the master//private String studyd;//★★Don't set public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Double getPrice() { return price; } public void setPrice(Double price) { this.price = price; } public Stud getS() { return s; } public void setS(Stud s) { this.s = s; } /* * When multi-table association, you should pay attention to a trap, that is, one party outputs the other party, and the other party in turn outputs the previous party, forming infinite recursion! */ @Override public String toString() { return "id=" + id + "," + name + "," + price;//The Stud object cannot be output here, otherwise infinite recursion}}Show student information page jsps/show.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %><html> <head> <title>Student Information Management</title> </head> <body> <h2>Student Information</h2> <c:forEach items="${studs}" var="x"> ${x.id},${x.name}<br/> </c:forEach> </body></html>Reproduction image:
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