针对customers表的通用查询操作举例
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https://www.bilibili.com/video/BV1eJ411c7rf?p=18
import io.github.jihch.bean.Customer;
import io.github.jihch.util.JDBCUtils;
import org.junit.Test;
import java.lang.reflect.Field;
import java.sql.*;
/**
* 针对于 Customers 表的查询操作
*/
public class CustomerForQuery {
@Test
public void testQueryForCustomers() {
String sql = "select id, name, email, birth from customers where id = ?";
Customer customer = queryForCustomers(sql, 2);
System.out.println(customer);
sql = "select name, email from customers where id = ?";
customer = queryForCustomers(sql, 2);
System.out.println(customer);
}
/**
* 针对 customers表的通用的查询操作
* @param sql
* @param args
* @throws Exception
*/
public Customer queryForCustomers(String sql, Object... args) {
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
Customer customer = null;
try {
conn = JDBCUtils.getConnection();
ps = conn.prepareStatement(sql);
for (int i = 0; i < args.length; i++) {
ps.setObject(i+1, args[i]);
}
rs = ps.executeQuery();
//获取结果集的元数据
ResultSetMetaData rsmd = rs.getMetaData();
//通过 ResultSetMetaData 获取结果集中的列数
int columnCount = rsmd.getColumnCount();
if (rs.next()) {
customer = new Customer();
//处理结果集一行数据中的每一列
for (int i = 0; i < columnCount; i++) {
//获取每个列的列名
String columnName = rsmd.getColumnName(i+1);
Object columnValue = rs.getObject(i + 1);
//给 customer 对象指定的某个属性，赋值为 value
Field field = Customer.class.getDeclaredField(columnName);
field.setAccessible(true);
field.set(customer, columnValue);
}
}//end if
} catch (SQLException e) {
throw new RuntimeException(e);
} catch (Exception e) {
throw new RuntimeException(e);
} finally {
JDBCUtils.closeResource(conn, ps, rs);
}
return customer;
}
}
Customer{id=2, name='汪峰', email='wf@126.com', birth=2010-02-02}
Customer{id=0, name='汪峰', email='wf@126.com', birth=null}