#创建数据库
CREATE DATABASE db5 CHARACTER SET utf8;
#使用数据库
USE db5;
#创建员工表
CREATE TABLE employee (
eid INT PRIMARY KEY AUTO_INCREMENT ,
ename VARCHAR (20), -- 员工姓名
age INT , -- 员工年龄
sex VARCHAR (6), -- 员工性别
salary DOUBLE , -- 薪水
empdate DATE -- 入职日期
);
#插入数据
INSERT INTO employee (eid, ename, age, sex, salary, empdate) VALUES(NULL,'李清
照',22,'女',4000,'2018-11-12');
INSERT INTO employee (eid, ename, age, sex, salary, empdate) VALUES(NULL,'林黛
玉',20,'女',5000,'2019-03-14');
INSERT INTO employee (eid, ename, age, sex, salary, empdate) VALUES(NULL,'杜
甫',40,'男',6000,'2020-01-01');
INSERT INTO employee (eid, ename, age, sex, salary, empdate) VALUES(NULL,'李白',25,'男',3000,'2017-10-01');

1.5 DBCP连接池

1.5.1 创建项目 导入 jar包

public class TestDBCP {
/*
* 测试DBCP连接池
* */
public static void main(String[] args) throws SQLException {
//1.从DBCP连接池中拿到连接
Connection con = DBCPUtils.getConnection();//2.获取Statement对象
Statement statement = con.createStatement();
//3.查询所有员工的姓名
String sql = "select ename from employee";
ResultSet resultSet = statement.executeQuery(sql);
//4.处理结果集
while(resultSet.next()){
String ename = resultSet.getString("ename");
System.out.println("员工姓名: " + ename);
}
//5.释放资源
DBCPUtils.close(con,statement,resultSet);
}
}

1.5.4 常见配置项

public class TestC3P0 {
//需求 查询姓名为李白的 记录
public static void main(String[] args) throws SQLException {
//1.获取连接
Connection con = C3P0Utils.getConnection();
//2.获取预处理对象
String sql = "select * from employee where ename = ?";
PreparedStatement ps = con.prepareStatement(sql);
//3.设置占位符的值
ps.setString(1,"李白");ResultSet resultSet = ps.executeQuery();
//4.处理结果集
while(resultSet.next()){
int eid = resultSet.getInt("eid");
String ename = resultSet.getString("ename");
int age = resultSet.getInt("age");
String sex = resultSet.getString("sex");
double salary = resultSet.getDouble("salary");
Date date = resultSet.getDate("empdate");
System.out.println(eid +" " + ename + " " + age +" " + sex +" " + salary +" "
+date);
}
//5.释放资源
C3P0Utils.close(con,ps,resultSet);
}
}

1.6.4 常见配置

public class DruidUtils {
//1.定义成员变量
public static DataSource dataSource;
//2.静态代码块
static{
try {
//3.创建属性集对象
Properties p = new Properties();
//4.加载配置文件 Druid 连接池不能够主动加载配置文件 ,需要指定文件
InputStream inputStream =
DruidUtils.class.getClassLoader().getResourceAsStream("druid.properties");
//5. 使用Properties对象的 load方法 从字节流中读取配置信息
p.load(inputStream);
//6. 通过工厂类获取连接池对象
dataSource = DruidDataSourceFactory.createDataSource(p);
} catch (Exception e) {
e.printStackTrace();
}
}//获取连接的方法
public static Connection getConnection(){
try {
return dataSource.getConnection();
} catch (SQLException e) {
e.printStackTrace();
return null;
}
}
//释放资源
public static void close(Connection con, Statement statement){
if(con != null && statement != null){
try {
statement.close();
//归还连接
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
public static void close(Connection con, Statement statement, ResultSet resultSet){
if(con != null && statement != null && resultSet != null){
try {
resultSet.close();
statement.close();
//归还连接
con.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}

1.7.3 测试工具类

public class TestDruid {// 需求 查询 薪资在3000 到 5000之间的员工的姓名
public static void main(String[] args) throws SQLException {
//1.获取连接
Connection con = DruidUtils.getConnection();
//2.获取Statement对象
Statement statement = con.createStatement();
//3.执行查询
ResultSet resultSet = statement.executeQuery("select ename from employee where salary
between 3000 and 5000");
//4.处理结果集
while(resultSet.next()){
String ename = resultSet.getString("ename");
System.out.println(ename);
}
//5.释放资源
DruidUtils.close(con,statement,resultSet);
}
}

2.2.2 JavaBean组件

4.3 使用JDBC 获取元数据

4.3.1 常用类介绍

public class TestMetaData {
//1.获取数据库相关的元数据信息 使用DatabaseMetaData
@Test
public void testDataBaseMetaData() throws SQLException {
//1.获取数据库连接对象 connection
Connection connection = DruidUtils.getConnection();
//2.获取代表数据库的 元数据对象 DatabaseMetaData
DatabaseMetaData metaData = connection.getMetaData();
//3.获取数据库相关的元数据信息
String url = metaData.getURL();
System.out.println("数据库URL: " + url);
String userName = metaData.getUserName();
System.out.println("当前用户: " + userName );
String productName = metaData.getDatabaseProductName();
System.out.println("数据库产品名: " + productName);
String version = metaData.getDatabaseProductVersion();
System.out.println("数据库版本: " + version);
String driverName = metaData.getDriverName();
System.out.println("驱动名称: " + driverName);
//判断当前数据库是否只允许只读
boolean b = metaData.isReadOnly(); //如果是 true 就表示 只读
if(b){
System.out.println("当前数据库只允许读操作!");
}else{
System.out.println("不是只读数据库");
}
connection.close();
}
//获取结果集中的元数据信息
@Test
public void testResultSetMetaData() throws SQLException {
//1.获取连接
Connection con = DruidUtils.getConnection();
//2.获取预处理对象
PreparedStatement ps = con.prepareStatement("select * from employee");
ResultSet resultSet = ps.executeQuery();
//3.获取结果集元素据对象
ResultSetMetaData metaData = ps.getMetaData();
//1.获取当前结果集 共有多少列
int count = metaData.getColumnCount();
System.out.println("当前结果集中共有: " + count + " 列");
//2.获结果集中 列的名称 和 类型
for (int i = 1; i <= count; i++) {
String columnName = metaData.getColumnName(i);
System.out.println("列名: "+ columnName);
String columnTypeName = metaData.getColumnTypeName(i);
System.out.println("类型: " +columnTypeName);
}
//释放资源
DruidUtils.close(con,ps,resultSet);
}
}

总结：