JavaWeb学习之路（二）--- 数据库操作优化

新建一个类ConnectionFactory，封装Connection；
新建一个文件properties文件dbconfig.properties，存放数据库配置数据；
示例代码：

// ConnectionFactory.java

package com.package.util;

import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.util.Properties;

public class ConnectionFactory {
private static String driver;
private static String dburl;
private static String  user;
private static String  password;
private static final ConnectionFactory factory = new ConnectionFactory();
private Connection conn;
static {
Properties prop = new Properties();
try {
InputStream in = ConnectionFactory.class.getClassLoader().getResourceAsStream("dbconfig.properties");
prop.load(in);
} catch (Exception e) {
System.out.println("=========配置文件读取错误========");
}
driver = prop.getProperty("driver");
dburl = prop.getProperty("dburl");
user = prop.getProperty("user");
password = prop.getProperty("password");

System.out.println("=========" + driver + "========");
System.out.println("=========" + dburl + "========");
System.out.println("=========" + user + "========");
System.out.println("=========" + password + "========");
}
private ConnectionFactory() {

}
public static ConnectionFactory getInstance() {
return factory;
}
public Connection makeConnection() {
try {
Class.forName(driver);
conn = DriverManager.getConnection(dburl, user, password);
} catch (Exception e) {
e.printStackTrace();
}
return conn;
}
}

// dbconfig.properties

driver = com.mysql.jdbc.Driver
dburl = jdbc:mysql://localhost:3306/test // test为数据库名称
user = root
password =

完整示例：数据库中有一个表（tab_user），使用模型通过接口的方式，操作数据库中的数据；

数据模型：

// IdEntity

package com.package.entity;

public abstract class IdEntity {
protected Long id;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
}

// user.java

package com.package.entity;

public class User extends IdEntity {

private String name;

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public String getPassword() {
return password;
}

public void setPassword(String password) {
this.password = password;
}

public String getEmail() {
return email;
}

public void setEmail(String email) {
this.email = email;
}

private String password;
private String email;

@Override
public String toString() {
return "User [name=" + name + ", password=" + password + ", email=" + email + ", id=" + id + "]";
}

}

接口文件：

// UserDao.java

package com.package.dao;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;

import com.package.entity.User;

public interface UserDao {

public v
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oid save(Connection conn, User user) throws SQLException;

public void update(Connection conn, Long id, User user) throws SQLException;

public void delete(Connection conn, User user) throws SQLException;

public ResultSet get(Connection conn, User user) throws SQLException;

}

// 接口实现文件：

// UserDaoImpl.java

package com.package.dao.impl;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import com.package.dao.UserDao;
import com.package.entity.User;

public class UserDaoImpl implements UserDao {

@Override
public void save(Connection conn, User user) throws SQLException {
// TODO Auto-generated method stub
PreparedStatement ps = conn.prepareCall("INSERT INTO tbl_user(name, password, email) VALUES (?,?,?)");
ps.setString(1, user.getName());
ps.setString(2, user.getPassword());
ps.setString(3, user.getEmail());
ps.execute();
}

@Override
public void update(Connection conn, Long id, User user) throws SQLException {
// TODO Auto-generated method stub
String updateSql = "UPDATE tbl_user SET name=?, password=?, email=? WHERE id=?";
PreparedStatement ps = conn.prepareStatement(updateSql);
ps.setString(1, user.getName());
ps.setString(2, user.getPassword());
ps.setString(3, user.getEmail());
ps.setLong(4, user.getId());
ps.execute();
}

@Override
public void delete(Connection conn, User user) throws SQLException {
// TODO Auto-generated method stub
PreparedStatement ps = conn.prepareStatement("DELETE FROM tbl_user WHERE id=?");
ps.setLong(1, user.getId());
ps.execute();
}

执行：

package com.package.test;

import java.sql.Connection;

import com.package.dao.UserDao;
import com.package.dao.impl.UserDaoImpl;
import com.package.entity.User;
import com.package.util.ConnectionFactory;

public class UserDaoTest {

public static void main(String[] args) {
// TODO Auto-generated method stub
Connection conn = null;
try {
conn = ConnectionFactory.getInstance().makeConnection();
conn.setAutoCommit(false);

UserDao userDao = new UserDaoImpl();
User tom = new User();
tom.setName("Tom");
tom.setPassword("12345");
tom.setEmail("4342323432@qq.com");
userDao.save(conn, tom);
conn.commit();
} catch (Exception e) {
try {
conn.rollback();
} catch (Exception e2) {

}
}
}
}