WEB框架研究笔记三（连接数据库）

前面的例子是EXTJS访问STRUTS的ACTION,ACTION里面的内容是写死的字符串。接下去的工作就是需要从数据库检索数据。

1.建立数据库，（采用ACCESS比较方便一点）

就建一个student的表吧简单点。

数据库放到发布目录下好了。

2.为这个表创建一个BEAN(其实是PO)

package bean;

public class Student {
    private int id;
    private String name;
    private String descn;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getDescn() {
        return descn;
    }
    public void setDescn(String descn) {
        this.descn = descn;
    }

}

3.写一个DAO

package dao;

import java.sql.Connection;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

import bean.Student;

public class StudentDao {
    public List getStudents(Connection con) throws SQLException{
        List students = new ArrayList();
        Statement st = con.createStatement();
        String sql = "select * from students";
        ResultSet rs = st.executeQuery(sql);
        while(rs.next()){
            Student student = new Student();
            student.setId(rs.getInt("id"));
            student.setName(rs.getString("name"));
            student.setDescn(rs.getString("descn"));
            students.add(student);
        }
        return students;
    }
    public int getStudentNum(Connection con) throws SQLException{
        Statement st = con.createStatement();
        String sql = "select count(*) from students ";
        ResultSet rs = st.executeQuery(sql);
        int num = 0 ;
        while(rs.next()){
            num = rs.getInt(1);
        }
        return num;
    }   

}

4.再写一个Service

package biz;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import util.DBUtil;
import dao.StudentDao;

public class StudentService {
    private StudentDao dao = new StudentDao();

    public List getStudents(){
        List students = null;
        Connection con = null;
        try {
            con = DBUtil.getConnection();
            students = dao.getStudents(con);
        } catch (Exception e) {
            students = new ArrayList();
            e.printStackTrace();
        } finally{
            try {
                if(con != null){con.close();}
            } catch (SQLException e) {}
        }
        return students;
    }
    public int getStudentNum(){
        int StudentNum = 0;
        Connection con = null;
        try{
            con = DBUtil.getConnection();
            StudentNum = dao.getStudentNum(con);
        } catch(Exception e){
            e.printStackTrace();
        }finally{
            try {
                if(con != null){con.close();}
            } catch (SQLException e) {}
        }
        return StudentNum;
    }

}

5.倒入上次写的两个UTIL:

package util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class DBUtil {

//    static String jdbcURL = "jdbc:mysql://127.0.0.1:3306/book";
//    static String jdbcDriver = "com.mysql.jdbc.Driver";
//    static String userName = "root";
//    static String password = "root";
    static String jdbcURL = "jdbc:odbc:Driver={MicroSoft Access Driver (*.mdb)};" +
      "DBQ=D:/HL/NoUse/Struts/strutsProj/WebContent/EmptyDb.mdb";
    static String jdbcDriver = "sun.jdbc.odbc.JdbcOdbcDriver";
    static String userName = "dba";
    static String password = "";
    /**
     * 获取数据库连接对象
     * @return 数据库连接对象
     * @throws ClassNotFoundException
     * @throws SQLException
     */
    public static Connection getConnection() throws ClassNotFoundException,
            SQLException {
        Class.forName(jdbcDriver);
        return DriverManager.getConnection(jdbcURL, userName, password);
    }
}

package util;

import java.util.ArrayList;
import java.util.List;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.io.xml.DomDriver;
/**
* Title: Ext JS 辅助类
* Description: 该类用于转换java对象为XML文件格式或JSON文件格式
* @author weijun
* @time: 2008.07.09
*/
public class ExtHelper {
    /**
     * 通过List生成XML数据
     * @param recordTotal 记录总数，不一定与beanList中的记录数相等
     * @param beanList 包含bean对象的集合
     * @return 生成的XML数据
     */
    public static String getXmlFromList(long recordTotal , List beanList) {
        Total total = new Total();
        total.setResults(recordTotal);
        List results = new ArrayList();
        results.add(total);
        results.addAll(beanList);
        XStream sm = new XStream(new DomDriver());
        for (int i = 0; i < results.size(); i++) {
            Class c = results.get(i).getClass();
            String b = c.getName();
            String[] temp = b.split("\\.");
            sm.alias(temp[temp.length - 1], c);
        }
        String xml = "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n"    + sm.toXML(results);
        return xml;
    }
    /**
     * 通过List生成XML数据
     * @param beanList 包含bean对象的集合
     * @return 生成的XML数据
     */
    public static String getXmlFromList(List beanList){
        return getXmlFromList(beanList.size(),beanList);
    }
    /**
     * 通过List生成JSON数据
     * @param recordTotal 记录总数，不一定与beanList中的记录数相等
     * @param beanList 包含bean对象的集合
     * @return 生成的JSON数据
     */
    public static String getJsonFromList(long recordTotal , List beanList){
        TotalJson total = new TotalJson();
        total.setTotalProperty(recordTotal);
        total.setRoot(beanList);
        JSONObject JsonObject = JSONObject.fromObject(total);
        System.out.print(JsonObject.toString());
        return JsonObject.toString();
    }
    /**
     * 通过List生成JSON数据
     * @param beanList 包含bean对象的集合
     * @return 生成的JSON数据
     */
    public static String getJsonFromList(List beanList){
        return getJsonFromList(beanList.size(),beanList);
    }
    /**
     * 通过bean生成JSON数据
     * @param bean bean对象
     * @return 生成的JSON数据
     */
    public static String getJsonFromBean(Object bean){
        JSONObject JsonObject = JSONObject.fromObject(bean);
        return JsonObject.toString();
    }
}

6.OK,准备工作结束，开始最后代码修改。

修改GridAction的Execute方法。

    public String execute() throws Exception
    {
        HttpServletResponse response = ServletActionContext.getResponse();
        try{
          List students = service.getStudents();
          String json = ExtHelper.getJsonFromList(service.getStudentNum(), students);

          response.setContentType("text/html; charset=UTF-8");
          System.out.print(json);
          response.getWriter().write(json);

        }
        catch (Exception ex){
        }       
        return null;
    }

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这样就实现了从数据库取数据返回前台的功能。

接下去就是要开始加入spring和hibernate