在网上找了许多文章，关于JDBC连接的杂七杂八，要么写的很复杂，所以自己总结了一下。
1.项目结构图
2.新建一个properites文件
用于jdbc加载数据库信息
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/jdbctest
username=root
password=root
jdbcPoolInitSize=103.新建jdbc连接池工具类JdbcPool
package com.test.util;
import java.io.InputStream;
import java.io.PrintWriter;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.SQLFeatureNotSupportedException;
import java.util.LinkedList;
import java.util.Properties;
import java.util.logging.Logger;
import javax.sql.DataSource;
/**
* * 原生的jdbc连接池，加载jdbc.properties文件
*/
public class JdbcPool implements DataSource {
/**
* * @Field: listConnections 使用LinkedList集合来存放数据库链接，
* 由于要频繁读写List集合，所以这里使用LinkedList存储数据库连接比较合适
*/
private static LinkedList<Connection> listConnections = new LinkedList<Connection>();
private static Connection conn;
// 在静态代码块中加载src/jdbc.properties数据库配置文件
static {
InputStream in = JdbcPool.class.getResourceAsStream("/jdbc.properties");
Properties prop = new Properties();
try {
prop.load(in);
String driver = prop.getProperty("driver");
String url = prop.getProperty("url");
String username = prop.getProperty("username");
String password = prop.getProperty("password");
// 数据库连接池的初始化连接数大小
int jdbcPoolInitSize = Integer.parseInt(prop.getProperty("jdbcPoolInitSize"));
// 加载数据库驱动
Class.forName(driver);
for (int i = 0; i < jdbcPoolInitSize; i++) {
conn = DriverManager.getConnection(url, username, password);
// System.out.println("获取到了连接" + conn);
// 将获取到的数据库连接加入到listConnections集合中，listConnections集合此时就是一个存放了数据库连接的连接池
listConnections.add(conn);
}
} catch (Exception e) {
throw new ExceptionInInitializerError(e);
}
}
/*
* * 获取数据库连接
*/
@Override
public Connection getConnection() throws SQLException {
// 如果数据库连接池中的连接对象的个数大于0
if (listConnections.size() > 0) {
// 从listConnections集合中获取一个数据库连接
System.out.println("listConnections数据库连接池大小是：" + listConnections.size());
// 返回Connection对象的代理对象
return (Connection) Proxy.newProxyInstance(JdbcPool.class.getClassLoader(), conn.getClass().getInterfaces(),
new InvocationHandler() {
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
if (!method.getName().equals("close")) {
System.out.println("获取到连接池连接对象......" + conn);
return method.invoke(conn, args);
} else {
// 如果调用的是Connection对象的close方法，就把conn还给数据库连接池
listConnections.add(conn);
// System.out.println(conn+ "，还给数据库连接池了");
// System.out.println("listConnections数据库连接池大小为"+ listConnections.size());
return null;
}
}
});
} else {
throw new RuntimeException("对不起，数据库忙");
}
}
//省略@Override方法
@Override
public PrintWriter getLogWriter() throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public void setLogWriter(PrintWriter out) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public void setLoginTimeout(int seconds) throws SQLException {
// TODO Auto-generated method stub
}
@Override
public int getLoginTimeout() throws SQLException {
// TODO Auto-generated method stub
return 0;
}
@Override
public Logger getParentLogger() throws SQLFeatureNotSupportedException {
// TODO Auto-generated method stub
return null;
}
@Override
public <T> T unwrap(Class<T> iface) throws SQLException {
// TODO Auto-generated method stub
return null;
}
@Override
public boolean isWrapperFor(Class<?> iface) throws SQLException {
// TODO Auto-generated method stub
return false;
}
@Override
public Connection getConnection(String username, String password) throws SQLException {
// TODO Auto-generated method stub
return null;
}
}3.新建JDBCUtil工具类
package com.test.util;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class JDBCUtil {
private static JdbcPool pool = new JdbcPool();
/**
* * 获取资源
*/
public static Connection getConnection() throws SQLException {
return pool.getConnection();
}
/**
* * 关闭资源
* * @param resultSet 查询返回的结果集，没有为空
* * @param statement
* * @param connection
*/
public static void close(ResultSet resultSet, Statement statement,
Connection connection) {
if (resultSet != null) {
try {
resultSet.close();
} catch (SQLException e) {
throw new RuntimeException(e);
}
resultSet = null;
}
if (statement != null) {
try {
statement.close();
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
throw new RuntimeException(e);
}
}
}
}4.数据库操作
package com.test.dao;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import com.test.util.JDBCUtil;
public class JDBCDao {
/**
* * 增加，删除，修改
*/
public static void insertOrDeleteOrUpdate(String sql) {
try {
Connection connection = JDBCUtil.getConnection();
PreparedStatement pst = connection.prepareStatement(sql);
int execute = pst.executeUpdate();
System.out.println("执行语句：" + sql + "," + execute + "行数据受影响");
JDBCUtil.close(null, pst, connection);
} catch (SQLException e) {
System.out.println("异常提醒：" + e);
}
}
/**
* * 查询，返回结果集
*/
public static List<Map<String, Object>> select(String sql) {
List<Map<String, Object>> returnResultToList = null;
try {
Connection connection = JDBCUtil.getConnection();
PreparedStatement pst = connection.prepareStatement(sql);
ResultSet resultSet = pst.executeQuery();
// returnResultToList = returnResultToList(resultSet);
JDBCUtil.close(resultSet, pst, connection);
} catch (SQLException e) {
System.out.println("异常提醒：" + e);
}
return returnResultToList;
}
/**
* * 数据返回集合 * @param resultSet * @return * @throws SQLException
*/
public static List<Map<String, Object>> returnResultToList(ResultSet resultSet) {
List<Map<String, Object>> values = null;
try {
// 键: 存放列的别名, 值: 存放列的值.
values = new ArrayList<>();
// 存放字段名
List<String> columnName = new ArrayList<>();
ResultSetMetaData rsmd = resultSet.getMetaData();
for (int i = 0; i < rsmd.getColumnCount(); i++) {
// 字段名
columnName.add(rsmd.getColumnLabel(i + 1));
}
System.out.println("表字段为：");
System.out.println(columnName);
System.out.println("表数据为：");
Map<String, Object> map = null;
// 处理 ResultSet, 使用 while 循环
while (resultSet.next()) {
map = new HashMap<>();
for (String column : columnName) {
Object value = resultSet.getObject(column);
map.put(column, value);
System.out.print(value + "\t");
}
// 把一条记录的 Map 对象放入准备的 List 中
values.add(map);
System.out.println();
}
} catch (SQLException e) {
System.out.println("异常提醒：" + e);
}
return values;
}
}