JDBC
2016-01-03 15:04
267 查看
补充
PreparedStatement 中使用mysql的like
请参考Using “like” wildcard in prepared statement
pstmt.setString(1, "%" + notes + "%");
PreparedStatement中使用日期
请参考Using setDate in PreparedStatement
ps.setDate(2, new java.sql.Date(endDate.getTime());
JDBC程序编写步骤
加载驱动打开连接
执行查询
处理结果
清理环境
JDBC编程之数据查询
package com.wz.jdbc;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Connection;
import java.sql.Statement;
public class JDBCTest {
public static void main(String[] args) {
String sql = "SELECT * FROM tbl_user";
Connection connection = null;
Statement statement = null;
ResultSet resultSet = null;
try {
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/jsp_db", "root", "");
statement = connection.createStatement();
resultSet = statement.executeQuery(sql);
while (resultSet.next()) {
System.out.print(resultSet.getInt("id")+" ");
System.out.print(resultSet.getString("name")+" ");
System.out.print(resultSet.getString("password")+" ");
System.out.print(resultSet.getString("email")+" ");
System.out.println();
}
} catch (Exception e) {
e.printStackTrace();
}finally {
try {
resultSet.close();
} catch (Exception e2) {
}
try {
statement.close();
} catch (Exception e2) {
}
try {
connection.close();
} catch (Exception e2) {
}
}
}
}console输出结果为：
1 xiaoming 123456 xiaoming@gmail.com 2 xiaozhang 123456 xiaozhang@gmail.com
JDBC编程之数据更新
package com.wz.jdbc;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;
public class JDBCTest {
//获取connection对象
public static Connection getConnection() {
Connection connection = null;
try {
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/jsp_db", "root", "");
} catch (Exception e) {
e.printStackTrace();
}
return connection;
}
//插入方法
public static void insert() {
Connection connection = getConnection();
try {
String sql = "INSERT INTO tbl_user(name, password, email)" +
"VALUES('Tom', '123456', 'tom@gmail.com')";
Statement statement = connection.createStatement();
int count = statement.executeUpdate(sql);
System.out.println("向用户表中插入了 "+ count + " 条记录");
connection.close();
} catch (Exception e) {
e.printStackTrace();
}
}
//更新方法
public static void update() {
Connection connection = getConnection();
try {
String sql = "UPDATE tbl_user SET email = 'tom@126.com' WHERE name = 'Tom'";
Statement statement = connection.createStatement();
int count = statement.executeUpdate(sql);
System.out.println("向用户表中更新了 "+ count + " 条记录");
connection.close();
} catch (Exception e) {
e.printStackTrace();
}
}
//删除记录
public static void delete() {
Connection connection = getConnection();
try {
String sql = "DELETE FROM tbl_user WHERE name = 'Tom'";
Statement statement = connection.createStatement();
int count = statement.executeUpdate(sql);
System.out.println("向用户表中删除了 "+ count + " 条记录");
connection.close();
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
//insert();
//update();
delete();
}
}JDBC编程之事务处理
事务的四个特征原子性
一致性
隔离性
持久性
事务的语句
开始事务：BEGIN TRANSACTION
提交事务：COMMIT TRANSACTION
回滚事务：ROLLBACK TRANSACTION
package com.wz.jdbc;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;
public class TransactionTest {
public static Connection getConnection() {
Connection connection = null;
try {
Class.forName("com.mysql.jdbc.Driver");
connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/jsp_db", "root", "");
} catch (Exception e) {
e.printStackTrace();
}
return connection;
}
//插入用户数据
public static void insertUserData() {
Connection connection = getConnection();
try {
String sql = "INSERT INTO tbl_user(id, name, password, email)" +
"VALUES(10, 'Tom', '123456', 'tom@gmail.com')";
Statement statement = connection.createStatement();
int count = statement.executeUpdate(sql);
System.out.println("向用户表插入了 "+ count + " 条记录");
} catch (Exception e) {
e.printStackTrace();
}
}
//向地址表中插入数据
public static void insertAddressData() {
Connection connection = getConnection();
try {
String sql = "INSERT INTO tbl_address(id, city, country, user_id)" +
"VALUES(1, 'shanghai', 'china', '10')";
Statement statement = connection.createStatement();
int count = statement.executeUpdate(sql);
System.out.println("向地址表插入了 "+ count + " 条记录");
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
insertUserData();
insertAddressData();
}
}在console中会输出错误信息：
向用户表插入了 1 条记录 com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry '1' for key 'PRIMARY'
在用户表中插入了数据，但是地址表中，却提示主键重复。这是一个严重的问题，只有部分的数据被插入。造成了数据完整性的问题。
修改代码，事务回滚
// 插入用户数据
public static void insertUserData(Connection connection) throws SQLException {
String sql = "INSERT INTO tbl_user(id, name, password, email)" + "VALUES(10, 'Tom', '123456', 'tom@gmail.com')";
Statement statement = connection.createStatement();
int count = statement.executeUpdate(sql);
System.out.println("向用户表插入了 " + count + " 条记录");
}
// 向地址表中插入数据
public static void insertAddressData(Connection connection) throws SQLException {
String sql = "INSERT INTO tbl_address(id, city, country, user_id)" + "VALUES(1, 'shanghai', 'china', '10')";
Statement statement = connection.createStatement();
int count = statement.executeUpdate(sql);
System.out.println("向地址表插入了 " + count + " 条记录");
}
public static void main(String[] args) {
Connection connection = null;
try {
connection = getConnection();
connection.setAutoCommit(false);//禁止自动提交
insertUserData(connection);
insertAddressData(connection);
connection.commit();
} catch (SQLException e) {
System.out.println("=============捕获到SQL异常================");
e.printStackTrace();
try {
connection.rollback();//回滚事务
} catch (Exception e2) {
e2.printStackTrace();
}
}finally {
//资源清理
try {
if (connection != null) {
connection.close();
}
} catch (Exception e2) {
e2.printStackTrace();
}
}
}这时控制台输出：
向用户表插入了 1 条记录
=============捕获到SQL异常================ com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry '1' for key 'PRIMARY'
查看用户表和地址表，会发现，并没有插入数据。
JDBC程序优化
在上述代码中，所有的数据库信息都是硬编码到Java代码中的，这是不可取的方式。把这些信息提取出来，放置到属性文件中。新建一个.properties文件
driver=com.mysql.jdbc.Driver dburl=jdbc:mysql://localhost:3306/jsp_db user=root password=
创建一个连接工厂类ConnectionFactory
package com.wz.util;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.util.Properties;
//连接工厂类
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 connection;//数据库连接
//静态代码块 只会执行一次
//数据库信息读取代码
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");
}
private ConnectionFactory(){
}
public static ConnectionFactory getInstance() {
return factory;
}
public Connection makeConnection() {
try {
Class.forName(driver);
connection = DriverManager.getConnection(dburl, user, password);
} catch (Exception e) {
e.printStackTrace();
}
return connection;
}
}在创建一个测试类ConnectionFactoryTest，测试下：
package com.wz.jdbc;
import java.sql.Connection;
import java.sql.SQLException;
import com.wz.util.ConnectionFactory;
public class ConnectionFactoryTest {
public static void main(String[] args) throws SQLException {
ConnectionFactory cf = ConnectionFactory.getInstance();//获取ConnectionFactory的一个实例
Connection connection = cf.makeConnection();//获取一个数据库连接
System.out.println(connection.getAutoCommit());//打印connection的一个属性
}
}console输出为：
true
进一步优化，创建DTO类
DAO叫数据访问对象DTO是数据传输对象
DAO通常是将非对象数据（如关系数据库中的数据）以对象的方式操纵。
DTO通常用于不同层（UI层、服务层或者域模型层）直接的数据传输，以隔离不同层，降低层间耦合
首先创建
IdEntity类，如下：
package com.wz.entity;
public abstract class IdEntity {
protected Long id;
public Long getId(){
return id;
}
public void setId(Long id){
this.id = id;
}
}再创建用户表对应的类，
User继承自
IdEntity：
package com.wz.entity;
public class User extends IdEntity {
private String name;
private String pasword;
private String email;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPasword() {
return pasword;
}
public void setPasword(String pasword) {
this.pasword = pasword;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
@Override
public String toString() {
return "User [name=" + name + ", pasword=" + pasword + ", email=" + email + ", id=" + id + "]";
}
}再创建地址表对应的类，
Address继承自
IdEntity
package com.wz.entity;
public class Address extends IdEntity {
private String city;
private String country;
private Long userId;
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public String getCountry() {
return country;
}
public void setCountry(String country) {
this.country = country;
}
public Long getUserId() {
return userId;
}
public void setUserId(Long userId) {
this.userId = userId;
}
@Override
public String toString() {
return "Address [city=" + city + ", country=" + country + ", userId=" + userId + ", id=" + id + "]";
}
}接下来，再创建DAO对象，用来对数据库访问。把数据库中的表转化为DTO类。
创建一个接口类
UserDao
package com.wz.dao;
import java.sql.Connection;
import java.sql.SQLException;
import com.wz.entity.User;
public interface UserDao {
//保存用户信息
public void save(Connection connection, User user) throws SQLException;
//更新用户信息
public void update(Connection connection, Long id, User user) throws SQLException;
//删除用户信息
public void delete(Connection connection, User user) throws SQLException;
}再创建一个
UserDaoImpl类，实现
UserDao：
package com.wz.dao.impl;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import com.wz.dao.UserDao;
import com.wz.entity.User;
public class UserDaoImpl implements UserDao {
/**
* 保存用户信息
*/
@Override
public void save(Connection connection, User user) throws SQLException {
PreparedStatement ps = connection.
prepareCall("INSERT INTO tbl_user(name, password, email) VALUES (?,?,?)");
ps.setString(1, user.getName());
ps.setString(2, user.getPasword());
ps.setString(3, user.getEmail());
ps.execute();
}
/**
* 根据用户指定的ID更新用户信息
*/
@Override
public void update(Connection connection,Long id, User user) throws SQLException {
String updateSql = "UPDATE tbl_user SET name = ?, password = ?, email = ? WHERE id = ?";
PreparedStatement ps = connection.prepareStatement(updateSql);
ps.setString(1, user.getName());
ps.setString(2, user.getPasword());
ps.setString(3, user.getEmail());
ps.setLong(4, id);
}
/**
* 删除指定的用户信息
*/
@Override
public void delete(Connection connection, User user) throws SQLException {
PreparedStatement ps = connection.prepareStatement("DELETE FROM tbl_user WHERE id = ?");
ps.setLong(1, user.getId());
ps.execute();
}
}新建一个测试类，来验证一下，如下：
package com.wz.test;
import java.sql.Connection;
import java.sql.SQLException;
import com.wz.dao.UserDao;
import com.wz.dao.impl.UserDaoImpl;
import com.wz.entity.User;
import com.wz.util.ConnectionFactory;
public class UserDaoTest {
public static void main(String[] args) {
Connection connection = null;
try {
connection = ConnectionFactory.getInstance().makeConnection();
connection.setAutoCommit(false);//关闭事务的自动提交
UserDao userDao = new UserDaoImpl();
User tom = new User();
tom.setName("Tom");
tom.setPasword("123456");
tom.setEmail("tom@gmail.com");
userDao.save(connection, tom);
connection.commit();
} catch (Exception e) {
try {
connection.rollback();
} catch (Exception e2) {
e.printStackTrace();
}
}
}
}
内容来自用户分享和网络整理，不保证内容的准确性，如有侵权内容，可联系管理员处理 
相关文章推荐
- jdbc中的Statement和PreparedStatement接口对象
- JDBC 数据库常用连接 链接字符串
- JDBC连接Access数据库的几种方式介绍
- JDBC程序更新数据库中记录的方法
- JDBC 程序的常见错误及调试方法
- 在Java的JDBC使用中设置事务回滚的保存点的方法
- Java中使用JDBC操作数据库简单实例
- Java加载JDBC驱动程序实例详解
- JSP使用JDBC完成动态验证及采用MVC完成数据查询的方法
- JSP基于JDBC的数据库连接类实例
- JSP中使用JDBC访问SQL Server 2008数据库示例
- jsp+jdbc实现连接数据库的方法
- 解析jdbc处理oracle的clob字段的详解
- JDBC数据库的使用操作总结
- jdbc操作mysql数据库实例
- JSP使用JDBC连接MYSQL数据库的方法
- Java开发Oracle数据库连接JDBC Thin Driver 的三种方法
- java使用jdbc操作数据库示例分享
- JDBC之PreparedStatement类中预编译的综合应用解析
- 基于Java回顾之JDBC的使用详解