Java-JDBC- 操作Mysql数据库（Druid连接池）
-
基础部分
导入druid的jar包https://mvnrepository.com/artifact/com.alibaba/druid/1.1.12
https://mvnrepository.com/artifact/com.alibaba/druid/1.1.12
使用数据库连接池Druid这里介绍两种连接方法
- 硬链接：
//硬编码
public void testHard() throws Exception {
//连接池对象
DruidDataSource druidDataSource = new DruidDataSource();
//设置参数（必须的:setUrl,setUsername,setPassword｜非必需的:setInitialSize...）
druidDataSource.setUrl("jdbc:mysql://localhost:3306/xxxxx");
druidDataSource.setUsername("root");
druidDataSource.setPassword("xxxx");
//获取连接
DruidPooledConnection connection = druidDataSource.getConnection();
//CRUD
//回收连接
connection.close();
}软连接：
首先准备一个druid.properties配置文件写入数据库的基本配置
#druid配置文件
driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/xxxxxx
username=root
password=xxxxpublic void testSoft() throws Exception {
Properties properties = new Properties();
InputStream rs = DruidUsePart.class.getClassLoader().getResourceAsStream("druid.properties");
properties.load(rs);
DataSource dataSource = DruidDataSourceFactory.createDataSource(properties);
Connection connection = dataSource.getConnection();
//CRUD
connection.close();
}-
实战部分
1.配置文件src/druid.properties
#druid配置文件
driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/xxxxxx
username=root
password=xxxx2.工具类
package druid;
import com.alibaba.druid.pool.DruidDataSourceFactory;
import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;
//这个工具类的作用就是用来给所有的SQL操作提供连接，和释放连接。
public class JDBCUtilsV2 {
private static DataSource dataSource=null;//连接池对象
private static ThreadLocal tl=new ThreadLocal<>();
static {
Properties properties = new Properties();
InputStream rs = JDBCUtilsV2.class.getClassLoader().getResourceAsStream("druid.properties");
try {
properties.load(rs);
} catch (IOException e) {
throw new RuntimeException(e);
}
try {
dataSource = DruidDataSourceFactory.createDataSource(properties);
} catch (Exception e) {
throw new RuntimeException(e);
}
}
//获取连接
public static Connection getConnection() throws SQLException {
Connection connection= tl.get();
if (connection==null){
connection=dataSource.getConnection();
tl.set(connection);
}
return connection;
}
//释放连接
public static void freeConnection() throws SQLException {
Connection connection = tl.get();
if (connection!=null){
tl.remove();//清空线程本地变量
connection.setAutoCommit(true);//回归事务状态（默认）
connection.close();
}
}
}
3.数据库如下 （id为主键且自增）
users
4.User类如下
@Data
public class User {
private int id;
private String userId;
private String username;
private String gender;
private int age;
private String password;
}5. DAO接口及其实现类，对所有表的操作（增、删、改、查）代码重复度很高，抽取公共代码，给这些DAO的实现类可以抽取一个公共的父类，我们称为BaseDao
package druid;
import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.ArrayList;
import java.util.List;
public class BaseDao {
/**
* @param sql 传入带占位符sql语句
* @param params 传入占位符的参数(Object...按列表使用)
* @return 返回影响行数
*/
public int executeUpdate(String sql, Object... params) throws Exception {
//获取连接
Connection connection = JDBCUtilsV2.getConnection();
PreparedStatement preparedStatement = connection.prepareStatement(sql);
for (int i = 1; i <= params.length; i++) {
preparedStatement.setObject(i, params[i - 1]);
}
int rows = preparedStatement.executeUpdate();
preparedStatement.close();
//回收连接考虑事务
if (connection.getAutoCommit()) {
//没有开启事务
JDBCUtilsV2.freeConnection();
}
return rows;
}
/**
* 通用的查询多个Javabean对象的方法，例如：多个User对象
* 这里的tClass接收的是T类型的Class对象
* @param tClass 如果查询员工信息，tClass代表Employee.class
* @param sql String类型的查询语句
* @param params 占位符参数
* @return
* @param
* @throws Exception
*/
public List executeQuery(Class tClass,String sql,Object... params)throws Exception{
//获取链接
Connection connection = JDBCUtilsV2.getConnection();
PreparedStatement preparedStatement = connection.prepareStatement(sql);
if (params!=null&¶ms.length!=0){
//占位符是从1-n，params是从0-n-1
for (int i = 0; i < params.length; i++) {
preparedStatement.setObject(i+1,params[i]);
}
}
ResultSet resultSet = preparedStatement.executeQuery();
ResultSetMetaData metaData = resultSet.getMetaData();//装当前结果集列的信息
int columnCount = metaData.getColumnCount();//列的数量
List list = new ArrayList<>();//一行数据对应一个T类型的对象
while (resultSet.next()) {
T t=tClass.newInstance();
for (int i = 1; i <= columnCount; i++) {
Object value = resultSet.getObject(i);//获取第i列的值（resultSet中的行列都从1开始数）
String propertyName = metaData.getColumnLabel(i);//select userId as ID,username as Name,gender,age,password from users;中可获取别名ID、Name
Field field = tClass.getDeclaredField(propertyName);
field.setAccessible(true);//打破private修饰
field.set(t,value);
}
list.add(t);
}
resultSet.close();
preparedStatement.close();
if(connection.getAutoCommit()){
JDBCUtilsV2.freeConnection();
}
return list;
}
}
7.举个例子
//在users中插入一条数据，结果如图8.1所示
@Test
public void testInsert() throws Exception {
UUID uuid = UUID.randomUUID();
String sql = "insert into users(userId,username,gender,age,password) values(?,?,?,?,?);";
int rows = executeUpdate(sql, uuid.toString().replace("-", ""), "zhangsan", "male", 25, "123456");
return rows;
}
//在users中查询所有数据，结果如图8.2所示
@Test
public void findAll() throws Exception {
String sql = "select * from users;";
List list = executeQuery(User.class, sql);
System.out.println(list.toString());
} 8.结果
图8.1插入结果
图8.2查询结果
10.对比
对于上述操作的对比可以见文章https://mp.csdn.net/mp_blog/creation/editor/129563984