java web项目操作mysql数据库的数据封装

在开发中， 我们常常会用到mysql数据库, 对操作mysql数据库的数据进入封装， 减少不必要代码的编写， 提高程序的逻辑性， 在开发项目时可以达到事关功倍的效果.

1. 在eclipse中， 新建一个动态web项目， File——>New——>Dynamic Web Project

2. 在src右键新建一个工具包util， 形如com.xxx.yyy.util， com表示商业性的， 也可是org(组织)， 或cn(中国)， xxx表示公司或组织或学校的简写，yyy表示项目应用的简写， 然后新建一个类， 名为ConnectionUtil.java

拷贝以下代码到ConnectionUtil.java里：

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.SQLException;
import javax.naming.Context;
import javax.naming.InitialContext;

public class ConnectionUtil {

private static DataSource ds = null;

static{
try{
Context initCtx = new InitialContext();
Context envCtx = (Context)initCtx.lookup("java:comp/env");
ds = (DataSource)envCtx.lookup("jdbc/WroxTC6");
}
catch(Exception ex) {
throw new RuntimeException(ex);
}
}

public static Connection getConnection() throws SQLException {
Connection conn = ds.getConnection();
return conn;
}

public static void returnConnection(Connection conn) {
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}

在项目的.../WebContent/META-INF/下新建一个context.xml文件， 拷贝以下代码进context.xml里：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<Context>
<Resource name="jdbc/WroxTC6" auth="Container"
type="javax.sql.DataSource"
maxActive="50"
maxIdle="100"
maxWait="10000"
username="root"
password="admin"
driverClassName="com.mysql.jdbc.Driver"
url="jdbc:mysql://localhost:3306/b2cmall?useUnicode=true&characterEncoding=UTF-8"
/>
</Context>

其中上面有三处要进入修改， username 填写你的mysql用户名， 默认是root， password 填写你的mysql用户对应的密码， 最后替换b2cmall为你要连接的数据库名称。

除了上面ConnectionUtil.java和context.xml文件外， 还要有连接mysql数据库的驱动包JDBC：mysql-connector-java-5.1.30-bin.jar，其中5.1.30是mysql-connector-java驱动包的版本号，  mysql-connector-java驱动包官方下载

将mysql-connector-java-5.1.30-bin.jar拷贝进.../WebContent/WEB-INF/lib/下即可。(ps:lib文件夹用来存在web项目需要使用的架包， 即类库)

3. ConnectionUtil.java、 context.xml、mysql-connector-java-5.1.30都准备后好， 开始编写DAO层

核心代码：

private Connection conn = null;
private PreparedStatement pstmt = null;
private ResultSet rs = null;

try{
conn = ConnectionUtil.getConnection();
//对mysql数据库进入操作
......

}catch(Exception e){
e.printStackTrace();
}finally{
try{
if(rs != null)
rs.close();
if(pstmt != null)
pstmt.close();
if(conn != null)
conn.close();
}catch(Exception ex){
ex.printStackTrace();
}
}

下面是一个简单的例子：

MemberDao.java代码(ps:此处暂时不考虑sql注入等问题， 所以暂时不过滤sql不安全字符)：

package com.b2c.model;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.util.ArrayList;import java.util.List;import com.b2c.common.Member;import com.b2c.util.ConnectionUtil;//数据库访问层--会员public class MemberDao {private Connection conn = null;private PreparedStatement pstmt = null;private ResultSet rs = null;/*** 注册，注意积分和级别的确定；密码需要通过加密算法处理后保存。* @param member* @return*/public int add(Member member){int val = 0;String sql = "";try{conn = ConnectionUtil.getConnection();sql = "INSERT INTO member(email,nick,password,credit,layerid,rDatetime,lastlogintime,lastloginip) VALUES(?,?,?,?,?,?,?,?)";pstmt = conn.prepareStatement(sql);pstmt.setString(1, member.getEmail());pstmt.setString(2, member.getNick());pstmt.setString(3, member.getPassword());pstmt.setInt(4, member.getCredit());pstmt.setInt(5, member.getLayerid());pstmt.setString(6, member.getrDatetime());pstmt.setString(7, member.getLastLoginTime());pstmt.setString(8, member.getLastLoginIp());val = pstmt.executeUpdate();}catch(Exception e){e.printStackTrace();}finally{try{if(rs != null)rs.close();if(pstmt != null)pstmt.close();if(conn != null)conn.close();}catch(Exception ex){ex.printStackTrace();}}return val;}/*** 会员信息修改* @param member* @return*/public int update(Member member){int val = 0;String sql = "";try{conn = ConnectionUtil.getConnection();sql = "UPDATE member SET email=?, nick=?, password=?, credit=?, layerid=?, rDatetime=?, lastlogintime=?, lastloginip=? WHERE id=?";pstmt = conn.prepareStatement(sql);pstmt.setString(1, member.getEmail());pstmt.setString(2, member.getNick());pstmt.setString(3, member.getPassword());pstmt.setInt(4, member.getCredit());pstmt.setInt(5, member.getLayerid());pstmt.setString(6, member.getrDatetime());pstmt.setString(7, member.getLastLoginTime());pstmt.setString(8, member.getLastLoginIp());pstmt.setInt(9, member.getId());val = pstmt.executeUpdate();}catch(Exception e){e.printStackTrace();}finally{try{if(rs != null)rs.close();if(pstmt != null)pstmt.close();if(conn != null)conn.close();}catch(Exception ex){ex.printStackTrace();}}return val;}/*** 根据id删除会员* @param id* @return*/public int delete(Integer id){int val = 0;String sql = "";try{conn = ConnectionUtil.getConnection();sql = "DELETE FROM member WHERE id=" + id;pstmt = conn.prepareStatement(sql);val = pstmt.executeUpdate();}catch(Exception e){e.printStackTrace();}finally{try{if(rs != null)rs.close();if(pstmt != null)pstmt.close();if(conn != null)conn.close();}catch(Exception ex){ex.printStackTrace();}}return val;}/*** 登录，验证用户的合法性。同时注意密码需要通过加密算法处理然后匹配。* @param username* @param pasword* @return*/public boolean validate(String username, String pasword){boolean flag = false;String sql = "";try{conn = ConnectionUtil.getConnection();sql = "SELECT * FROM member WHERE email=? AND password=?";pstmt = conn.prepareStatement(sql);pstmt.setString(1, username);pstmt.setString(2, pasword);rs = pstmt.executeQuery();if(rs.next())flag = true;}catch(Exception e){e.printStackTrace();}finally{try{if(rs != null)rs.close();if(pstmt != null)pstmt.close();if(conn != null)conn.close();}catch(Exception ex){ex.printStackTrace();}}return flag;}/*** 重置密码，将某个用户的密码重置为新密码* @param username* @param password* @return*/public int resetPassword(String email, String password){int val = 0;String sql = "";try{conn = ConnectionUtil.getConnection();sql = "UPDATE member set password=? WHERE email=?";pstmt = conn.prepareStatement(sql);pstmt.setString(1, password);pstmt.setString(2, email);val = pstmt.executeUpdate();}catch(Exception e){e.printStackTrace();}finally{try{if(rs != null)rs.close();if(pstmt != null)pstmt.close();if(conn != null)conn.close();}catch(Exception ex){ex.printStackTrace();}}return val;}/*** 根据id查询会员* @param id* @return*/public Member findById(Integer id){Member memb = null;String sql = "";try{conn = ConnectionUtil.getConnection();sql = "SELECT * FROM member WHERE id=" + id;pstmt = conn.prepareStatement(sql);rs = pstmt.executeQuery();if(rs.next()){memb = new Member();memb.setId(rs.getInt("id"));memb.setEmail(rs.getString("email"));memb.setNick(rs.getString("nick"));memb.setPassword(rs.getString("password"));memb.setCredit(rs.getInt("credit"));memb.setLayerid(rs.getInt("layerid"));memb.setrDatetime(rs.getString("rDatetime"));memb.setLastLoginTime(rs.getString("lastlogintime"));memb.setLastLoginIp(rs.getString("lastloginip"));}}catch(Exception e){e.printStackTrace();}finally{try{if(rs != null)rs.close();if(pstmt != null)pstmt.close();if(conn != null)conn.close();}catch(Exception ex){ex.printStackTrace();}}return memb;}/*** 根据邮箱email查询会员* @param email* @return*/public Member findByEmail(String email){Member memb = null;String sql = "";try{conn = ConnectionUtil.getConnection();sql = "SELECT * FROM member WHERE email=?";pstmt = conn.prepareStatement(sql);pstmt.setString(1, email);rs = pstmt.executeQuery();if(rs.next()){memb = new Member();memb.setId(rs.getInt("id"));memb.setEmail(rs.getString("email"));memb.setNick(rs.getString("nick"));memb.setPassword(rs.getString("password"));memb.setCredit(rs.getInt("credit"));memb.setLayerid(rs.getInt("layerid"));memb.setrDatetime(rs.getString("rDatetime"));memb.setLastLoginTime(rs.getString("lastlogintime"));memb.setLastLoginIp(rs.getString("lastloginip"));}}catch(Exception e){e.printStackTrace();}finally{try{if(rs != null)rs.close();if(pstmt != null)pstmt.close();if(conn != null)conn.close();}catch(Exception ex){ex.printStackTrace();}}return memb;}/*** 根据查询条件分布查询会员* @param sqlCause* @param startindex* @param size* @return*/public List<Member> findList(String sqlCause, int startindex, int size){List<Member> list = null;Member memb = null;String sql = "";try{list = new ArrayList<Member>();conn = ConnectionUtil.getConnection();sql = "SELECT * FROM member ";if(!sqlCause.equals(""))sql += "WHERE " + sqlCause;sql += " LIMIT ?,?";pstmt = conn.prepareStatement(sql);pstmt.setInt(1, startindex);pstmt.setInt(2, size);rs = pstmt.executeQuery();while(rs.next()){memb = new Member();memb.setId(rs.getInt("id"));memb.setEmail(rs.getString("email"));memb.setNick(rs.getString("nick"));memb.setPassword(rs.getString("password"));memb.setCredit(rs.getInt("credit"));memb.setLayerid(rs.getInt("layerid"));memb.setrDatetime(rs.getString("rDatetime"));memb.setLastLoginTime(rs.getString("lastlogintime"));memb.setLastLoginIp(rs.getString("lastloginip"));list.add(memb);}}catch(Exception e){e.printStackTrace();}finally{try{if(rs != null)rs.close();if(pstmt != null)pstmt.close();if(conn != null)conn.close();}catch(Exception ex){ex.printStackTrace();}}return list;}/*** 查找所有会员* @return*/public List<Member> findList(){List<Member> list = null;Member memb = null;String sql = "";try{list = new ArrayList<Member>();conn = ConnectionUtil.getConnection();sql = "SELECT * FROM member";pstmt = conn.prepareStatement(sql);rs = pstmt.executeQuery();while(rs.next()){memb = new Member();memb.setId(rs.getInt("id"));memb.setEmail(rs.getString("email"));memb.setNick(rs.getString("nick"));memb.setPassword(rs.getString("password"));memb.setCredit(rs.getInt("credit"));memb.setLayerid(rs.getInt("layerid"));memb.setrDatetime(rs.getString("rDatetime"));memb.setLastLoginTime(rs.getString("lastlogintime"));memb.setLastLoginIp(rs.getString("lastloginip"));list.add(memb);}}catch(Exception e){e.printStackTrace();}finally{try{if(rs != null)rs.close();if(pstmt != null)pstmt.close();if(conn != null)conn.close();}catch(Exception ex){ex.printStackTrace();}}return list;}/*** 根据查询条件获取记录数* @param sqlCause* @return*/public int findCount(String sqlCause){int count = 0;String sqlQuery = "";try{conn = ConnectionUtil.getConnection();sqlQuery = "SELECT count(*) FROM member ";if(!sqlCause.equals(""))sqlQuery += "WHERE " + sqlCause;pstmt = conn.prepareStatement(sqlQuery);rs = pstmt.executeQuery();rs.next();count = rs.getInt(1);}catch(Exception e){e.printStackTrace();}finally{try{if(rs != null)rs.close();if(pstmt != null)pstmt.close();if(conn != null)conn.close();}catch(Exception ex){ex.printStackTrace();}}return count;}}

4.  本人打包了struts2所需架包及上面的提及到的ConnectionUtil.java、 context.xml、mysql-connector-java-5.1.30， 点击下载

5. 以上的代码还不能更好地体验数据的封装， 比如上面不断重复以下代码：

try{if(rs != null)rs.close();if(pstmt != null)pstmt.close();if(conn != null)conn.close();}catch(Exception ex){ex.printStackTrace();}

对于重复的代码， 我们应该合并为一个方法即可。下面在此进行进一步优化...结构如下：

上面DBConnectionUtil.java和db.properties两个文件是关键， db.properties封装mysql的用户名、密码、jdbc驱动包、数据库源，文件后缀名一定要为.properties.

db.properties代码内容如下：

user=rooturl=jdbc\:mysql\://localhost\:3306/b2cmall?useUnicode=true&characterEncoding=UTF-8password=admindriver=com.mysql.jdbc.Driver

DBConnectionUtil.java封装了连接mysql数据库的驱动管理实例， 代码如下：

import java.io.IOException;import java.io.InputStream;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.util.Properties;public class DBConnectionUtil {private static String user;private static String password;private static String url;private static String driver;static {try {ClassLoader classLoader = DBConnectionUtil.class.getClassLoader();InputStream is = classLoader.getResourceAsStream("config/props/db.properties");Properties props = new Properties();props.load(is);url = props.getProperty("url");user = props.getProperty("user");password = props.getProperty("password");driver = props.getProperty("driver");// 注册驱动Class.forName(driver);} catch (ClassNotFoundException e) {e.printStackTrace();throw new RuntimeException("找不到驱动");} catch (IOException e) {e.printStackTrace();throw new RuntimeException("加载properties文件错误");}}/*** 获取连接* @return* @throws Exception*/public static Connection getConnection() throws Exception {return DriverManager.getConnection(url, user, password);}/*** 关闭连接* @param conn* @param pstmt* @param rs* @throws Exception*/public static void close(Connection conn, PreparedStatement pstmt, ResultSet rs) throws Exception {if (rs != null)rs.close();if (pstmt != null)pstmt.close();if (conn != null)conn.close();}}

将上面的DBConnectionUtil.java、db.properties、和mysql-connector-java-5.1.30-bin.jar驱动包放置到各自相应的位置即可， 使用示例如下：

MemberDao.java代码内容(增强版)：

import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.util.ArrayList;import java.util.List;import com.gditc.b2cmall.common.Member;import com.gditc.b2cmall.util.DBConnectionUtil;//数据库访问层--会员public class MemberDao {private Connection conn = null;private PreparedStatement pstmt = null;private ResultSet rs = null;/*** 注册，注意积分和级别的确定；密码需要通过加密算法处理后保存。* @param member* @return* @throws Exception*/public int add(Member member) throws Exception{int val = 0;String sql = "";try{conn = DBConnectionUtil.getConnection();sql = "INSERT INTO member(email,nick,password,credit,layerid,rDatetime,lastlogintime,lastloginip) VALUES(?,?,?,?,?,?,?,?)";pstmt = conn.prepareStatement(sql);pstmt.setString(1, member.getEmail());pstmt.setString(2, member.getNick());pstmt.setString(3, member.getPassword());pstmt.setInt(4, member.getCredit());pstmt.setInt(5, member.getLayerid());pstmt.setString(6, member.getrDatetime());pstmt.setString(7, member.getLastLoginTime());pstmt.setString(8, member.getLastLoginIp());val = pstmt.executeUpdate();}catch(Exception e){e.printStackTrace();}finally{DBConnectionUtil.close(conn, pstmt, rs);}return val;}/*** 会员信息修改* @param member* @return* @throws Exception*/public int update(Member member) throws Exception {int val = 0;String sql = "";try {conn = DBConnectionUtil.getConnection();sql = "UPDATE member SET email=?, nick=?, password=?, credit=?, layerid=?, rDatetime=?, lastlogintime=?, lastloginip=? WHERE id=?";pstmt = conn.prepareStatement(sql);pstmt.setString(1, member.getEmail());pstmt.setString(2, member.getNick());pstmt.setString(3, member.getPassword());pstmt.setInt(4, member.getCredit());pstmt.setInt(5, member.getLayerid());pstmt.setString(6, member.getrDatetime());pstmt.setString(7, member.getLastLoginTime());pstmt.setString(8, member.getLastLoginIp());pstmt.setInt(9, member.getId());val = pstmt.executeUpdate();} catch(Exception e) {e.printStackTrace();} finally {DBConnectionUtil.close(conn, pstmt, rs);}return val;}/*** 根据id删除会员* @param id* @return* @throws Exception*/public int delete(Integer id) throws Exception {int val = 0;String sql = "";try {conn = DBConnectionUtil.getConnection();sql = "DELETE FROM member WHERE id=" + id;pstmt = conn.prepareStatement(sql);val = pstmt.executeUpdate();} catch(Exception e) {e.printStackTrace();} finally {DBConnectionUtil.close(conn, pstmt, rs);}return val;}/*** 登录，验证用户的合法性。同时注意密码需要通过加密算法处理然后匹配。* @param username* @param pasword* @return* @throws Exception*/public boolean validate(String username, String pasword) throws Exception {boolean flag = false;String sql = "";try {conn = DBConnectionUtil.getConnection();sql = "SELECT * FROM member WHERE email=? AND password=?";pstmt = conn.prepareStatement(sql);pstmt.setString(1, username);pstmt.setString(2, pasword);rs = pstmt.executeQuery();if(rs.next())flag = true;} catch(Exception e) {e.printStackTrace();} finally {DBConnectionUtil.close(conn, pstmt, rs);}return flag;}/*** 重置密码，将某个用户的密码重置为新密码* @param username* @param password* @return* @throws Exception*/public int resetPassword(String email, String password) throws Exception {int val = 0;String sql = "";try {conn = DBConnectionUtil.getConnection();sql = "UPDATE member set password=? WHERE email=?";pstmt = conn.prepareStatement(sql);pstmt.setString(1, password);pstmt.setString(2, email);val = pstmt.executeUpdate();} catch(Exception e) {e.printStackTrace();} finally {DBConnectionUtil.close(conn, pstmt, rs);}return val;}/*** 根据id查询会员* @param id* @return* @throws Exception*/public Member findById(Integer id) throws Exception {Member memb = null;String sql = "";try{conn = DBConnectionUtil.getConnection();sql = "SELECT * FROM member WHERE id=" + id;pstmt = conn.prepareStatement(sql);rs = pstmt.executeQuery();if(rs.next()){memb = new Member();memb.setId(rs.getInt("id"));memb.setEmail(rs.getString("email"));memb.setNick(rs.getString("nick"));memb.setPassword(rs.getString("password"));memb.setCredit(rs.getInt("credit"));memb.setLayerid(rs.getInt("layerid"));memb.setrDatetime(rs.getString("rDatetime"));memb.setLastLoginTime(rs.getString("lastlogintime"));memb.setLastLoginIp(rs.getString("lastloginip"));}} catch(Exception e) {e.printStackTrace();} finally {DBConnectionUtil.close(conn, pstmt, rs);}return memb;}/*** 根据邮箱email查询会员* @param email* @return* @throws Exception*/public Member findByEmail(String email) throws Exception {Member memb = null;String sql = "";try {conn = DBConnectionUtil.getConnection();sql = "SELECT * FROM member WHERE email=?";pstmt = conn.prepareStatement(sql);pstmt.setString(1, email);rs = pstmt.executeQuery();if(rs.next()){memb = new Member();memb.setId(rs.getInt("id"));memb.setEmail(rs.getString("email"));memb.setNick(rs.getString("nick"));memb.setPassword(rs.getString("password"));memb.setCredit(rs.getInt("credit"));memb.setLayerid(rs.getInt("layerid"));memb.setrDatetime(rs.getString("rDatetime"));memb.setLastLoginTime(rs.getString("lastlogintime"));memb.setLastLoginIp(rs.getString("lastloginip"));}} catch(Exception e) {e.printStackTrace();} finally {DBConnectionUtil.close(conn, pstmt, rs);}return memb;}/*** 根据查询条件分布查询会员* @param sqlCause* @param startindex* @param size* @return* @throws Exception*/public List<Member> findList(String sqlCause, int startindex, int size) throws Exception {List<Member> list = null;Member memb = null;String sql = "";try {list = new ArrayList<Member>();conn = DBConnectionUtil.getConnection();sql = "SELECT * FROM member ";if(!sqlCause.equals(""))sql += "WHERE " + sqlCause;sql += " LIMIT ?,?";pstmt = conn.prepareStatement(sql);pstmt.setInt(1, startindex);pstmt.setInt(2, size);rs = pstmt.executeQuery();while(rs.next()) {memb = new Member();memb.setId(rs.getInt("id"));memb.setEmail(rs.getString("email"));memb.setNick(rs.getString("nick"));memb.setPassword(rs.getString("password"));memb.setCredit(rs.getInt("credit"));memb.setLayerid(rs.getInt("layerid"));memb.setrDatetime(rs.getString("rDatetime"));memb.setLastLoginTime(rs.getString("lastlogintime"));memb.setLastLoginIp(rs.getString("lastloginip"));list.add(memb);}} catch(Exception e) {e.printStackTrace();} finally {DBConnectionUtil.close(conn, pstmt, rs);}return list;}/*** 查找所有会员* @return* @throws Exception*/public List<Member> findList() throws Exception {List<Member> list = null;Member memb = null;String sql = "";try{list = new ArrayList<Member>();conn = DBConnectionUtil.getConnection();sql = "SELECT * FROM member";pstmt = conn.prepareStatement(sql);rs = pstmt.executeQuery();while(rs.next()) {memb = new Member();memb.setId(rs.getInt("id"));memb.setEmail(rs.getString("email"));memb.setNick(rs.getString("nick"));memb.setPassword(rs.getString("password"));memb.setCredit(rs.getInt("credit"));memb.setLayerid(rs.getInt("layerid"));memb.setrDatetime(rs.getString("rDatetime"));memb.setLastLoginTime(rs.getString("lastlogintime"));memb.setLastLoginIp(rs.getString("lastloginip"));list.add(memb);}} catch(Exception e) {e.printStackTrace();} finally {DBConnectionUtil.close(conn, pstmt, rs);}return list;}/*** 根据查询条件获取记录数* @param sqlCause* @return* @throws Exception*/public int findCount(String sqlCause) throws Exception {int count = 0;String sqlQuery = "";try {conn = DBConnectionUtil.getConnection();sqlQuery = "SELECT count(*) FROM member ";if(!sqlCause.equals(""))sqlQuery += "WHERE " + sqlCause;pstmt = conn.prepareStatement(sqlQuery);rs = pstmt.executeQuery();rs.next();count = rs.getInt(1);} catch(Exception e) {e.printStackTrace();} finally {DBConnectionUtil.close(conn, pstmt, rs);}return count;}}

至此， 我们减少了更多重复代码的编写，逻辑性也更加良好， 更好地体验到数据封装的理念...

6. OK. Enjoy it!!!