2：Jdbc工具类
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版本一：最基本的Jdbc工具类
public class JdbcUtil {
private static String url = "jdbc:mysql://localhost:3306/db_data_show_5?useSSL=false&serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=UTF8&autoReconnect=true&failOverReadOnly=false";
private static String password = "root";
private static String user = "root";
static {
try {
Class.forName("com.mysql.cj.jdbc.Driver");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
/**
* 释放资源
*
* @param rs
* @param stmt
* @param conn
*/
public static void release(ResultSet rs, Statement stmt, Connection conn) {
try {
if (rs != null) {
rs.close();
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (stmt != null) {
stmt.close();
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (conn != null) {
conn.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
/**
* 获取连接
*
* @return
* @throws SQLException
*/
public static Connection getConnection() throws SQLException {
final Connection conn = DriverManager.getConnection(url, user, password);
return conn;
}
}
版本二：抽取连接信息后的工具类
- 第一步：在resources目录下创建mysql.properties文件
url=jdbc:mysql://localhost:3306/db_data_show_5?useSSL=false&serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=UTF8&autoReconnect=true&failOverReadOnly=false
password=root
user=root
- 第二步：使用配置文件的工具类
public class JdbcUtil {
private static String url ;
private static String password;
private static String user;
static {
try {
Class.forName("com.mysql.cj.jdbc.Driver");
final Properties properties = new Properties();
//getResourceAsStream：读取文件，在JavaSE和javaWeb中都可以用，注意路径问题
final InputStream is = JdbcUtil.class.getResourceAsStream("/mysql.properties");
properties.load(is);
url = properties.getProperty("url");
user = properties.getProperty("user");
password = properties.getProperty("password");
is.close();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
/**
* 获取连接
*
* @return
* @throws SQLException
*/
public static Connection getConnection() throws SQLException {
final Connection conn = DriverManager.getConnection(url, user, password);
return conn;
}
/**
* 释放资源
*
* @param rs
* @param stmt
* @param conn
*/
public static void release(ResultSet rs, Statement stmt, Connection conn) {
try {
if (rs != null) {
rs.close();
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (stmt != null) {
stmt.close();
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (conn != null) {
conn.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
public static void main(String[] args) throws SQLException {
final Connection conn = getConnection();
System.out.println(conn);
}
}
版本三：添加Druid数据库连接支持
- 添加Druid依赖
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>1.1.17</version>
</dependency>
- 修改mysql.properties
driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/db_data_show_5?useSSL=false&serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=UTF8&autoReconnect=true&failOverReadOnly=false
username=root
password=root
# 初始化时创建的连接的个数
initialSize=10
# 处于活跃状态的连接的个数
maxActive=20
# 连接最多等待时长
maxWait=6000
- 修改JdbcUtil：
public class JdbcUtil {
private static DataSource dataSource;
static {
try {
Class.forName("com.mysql.cj.jdbc.Driver");
final Properties properties = new Properties();
//getResourceAsStream：读取文件，在JavaSE和javaWeb中都可以用，注意路径问题
final InputStream is = JdbcUtil.class.getResourceAsStream("/mysql.properties");
properties.load(is);
dataSource = DruidDataSourceFactory.createDataSource(properties);
is.close();
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 获取连接
*
* @return
* @throws SQLException
*/
public static Connection getConnection() throws SQLException {
final Connection conn =dataSource.getConnection();
return conn;
}
/**
* 释放资源
*
* @param rs
* @param stmt
* @param conn
*/
public static void release(ResultSet rs, Statement stmt, Connection conn) {
try {
if (rs != null) {
rs.close();
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (stmt != null) {
stmt.close();
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (conn != null) {
conn.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
public static void main(String[] args) throws SQLException {
final Connection conn = getConnection();
System.out.println(conn);
}
}
版本四：添加LocalThread以支持并发
public class JdbcUtil {
private static DataSource dataSource;
private static ThreadLocal<Connection> threadLocal = new ThreadLocal<>();
static {
try {
Class.forName("com.mysql.cj.jdbc.Driver");
final Properties properties = new Properties();
//getResourceAsStream：读取文件，在JavaSE和javaWeb中都可以用，注意路径问题
final InputStream is = JdbcUtil.class.getResourceAsStream("/mysql.properties");
properties.load(is);
dataSource = DruidDataSourceFactory.createDataSource(properties);
is.close();
} catch (Exception e) {
throw new RuntimeException("读取配置文件错误");
}
}
/**
* 获取连接
*
* @return
* @throws SQLException
*/
public static Connection getConnection() {
Connection conn = threadLocal.get();
try {
if (conn == null || conn.isClosed()) {
conn = dataSource.getConnection();
threadLocal.set(conn);
}
} catch (SQLException e) {
throw new RuntimeException("获取连接失败！");
}
return conn;
}
/**
* 释放资源
*
* @param rs
* @param stmt
* @param conn
*/
public static void release(ResultSet rs, Statement stmt, Connection conn) {
try {
if (rs != null) {
rs.close();
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (stmt != null) {
stmt.close();
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (conn != null) {
conn.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
public static void main(String[] args) throws SQLException {
final Connection conn = getConnection();
System.out.println(conn);
}
}
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