java连接mysql
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2024-01-27 12:04:46
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1.首先要下载数据驱动jar包地址:http://www.mysql.com/downloads/connector/j/
2.将jar导入myeclipse中,点击添加jar包
3.创建一个ConnectionDB.java文件
/*
* 连接数据库
*/
public class ConnectionDB {
/**
* 数据库驱动类名称
*/
private static final String DRIVER = "com.mysql.jdbc.Driver";
/**
* 连接字符串
*/
private static final String URLSTR = "jdbc:mysql://localhost:3306/shop";
/**
* 用户名
*/
private static final String USERNAME = "root";
/**
* 密码
*/
private static final String USERPASSWORD = "admin";
/**
* 创建数据库连接对象
*/
private Connection connnection = null;
/**
* 创建PreparedStatement对象
*/
private PreparedStatement preparedStatement = null;
/**
* 创建结果集对象
*/
private ResultSet resultSet = null;
/**
*加载数据库的驱动
*/
static {
try {
Class.forName(DRIVER);
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
/**
* 获取数据库连接
* @return 数据库连接
*/
public Connection getConnection() {
try {
//获取连接
connnection = DriverManager.getConnection(URLSTR, USERNAME,USERPASSWORD);
} catch (SQLException e) {
System.out.println(e.getMessage());
}
return connnection;
}
/**
* insert update delete SQL语句的执行的统一方法
* @param sql SQL语句
* @param params 参数数组,若没有参数则为null
* @return 受影响的行数
*/
public int executeUpdate(String sql, Object[] params) {
// 受影响的行数
int affectedLine = 0;
try {
//获得连接
connnection = this.getConnection();
//调用SQL
preparedStatement = connnection.prepareStatement(sql);
// 参数赋值
if (params != null) {
for (int i = 0; i < params.length; i++) {
preparedStatement.setObject(i + 1, params[i]);
}
}
// 执行
affectedLine = preparedStatement.executeUpdate();
} catch (SQLException e) {
System.out.println(e.getMessage());
} finally {
// 释放资源
closeAll();
}
return affectedLine;
}
/**
* SQL 查询将查询结果直接放入ResultSet中
* @param sql SQL语句
* @param params 参数数组,若没有参数则为null
* @return 结果集
*/
private ResultSet executeQueryRS(String sql, Object[] params) {
try {
// 获得连接
connnection = this.getConnection();
// 调用SQL
preparedStatement = connnection.prepareStatement(sql);
// 参数赋值
if (params != null) {
for (int i = 0; i < params.length; i++) {
preparedStatement.setObject(i + 1, params[i]);
}
}
// 执行
resultSet = preparedStatement.executeQuery();
} catch (SQLException e) {
System.out.println(e.getMessage());
}
return resultSet;
}
/**
* 获取结果集,并将结果放在List中
* @param sql SQL语句
* @return List 结果集
*/
public List<Object> excuteQuery(String sql, Object[] params) {
// 执行SQL获得结果集
ResultSet rs = executeQueryRS(sql, params);
// 创建ResultSetMetaData对象
ResultSetMetaData rsmd = null;
// 结果集列数
int columnCount = 0;
try {
rsmd = rs.getMetaData();
// 获得结果集列数
columnCount = rsmd.getColumnCount();
} catch (SQLException e1) {
System.out.println(e1.getMessage());
}
// 创建List
List<Object> list = new ArrayList<Object>();
try {
// 将ResultSet的结果保存到List中
while (rs.next()) {
Map<String, Object> map = new HashMap<String, Object>();
for (int i = 1; i <= columnCount; i++) {
map.put(rsmd.getColumnLabel(i), rs.getObject(i));
}
list.add(map);
}
} catch (SQLException e) {
System.out.println(e.getMessage());
} finally {
closeAll();
}
return list;
}
/**
* 关闭所有资源
*/
private void closeAll() {
// 关闭结果集对象
if (resultSet != null) {
try {
resultSet.close();
} catch (SQLException e) {
System.out.println(e.getMessage());
}
}
// 关闭PreparedStatement对象
if (preparedStatement != null) {
try {
preparedStatement.close();
} catch (SQLException e) {
System.out.println(e.getMessage());
}
}
// 关闭Connection 对象
if (connnection != null) {
try {
connnection.close();
} catch (SQLException e) {
System.out.println(e.getMessage());
}
}
}
}
4.直接传入sql语句即可
5.调用
public static void main(String[] args) {
ConnectionDB connectionDB=new ConnectionDB();
String sql="select * from person";
List<Object> excuteQuery = connectionDB.excuteQuery(sql, null);
for (int i = 0; i < excuteQuery.size(); i++) {
Map<String, Object> map = (Map<String, Object>) excuteQuery.get(i);
System.out.println(map.get("id"));
}
}
6.结果