第二十九章 參數的元數據信息

靈活的傳入sql語句，和sql語句的參數

報錯：java.sql.SQLException: Parameter metadata not available for the given statement

原因不明

package cn.itcast.jdbc;

import java.sql.Connection;
import java.sql.Date;
import java.sql.ParameterMetaData;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;


public class ParameterMetaTest {
	
	
	public static void main(String[] args) throws SQLException{
		String sql = "select name,birthday from user where name =? and birthday<? and money>?";
		Object[] params = new Object[]{"list", new Date(System.currentTimeMillis()), 100f};
		ParameterMetaTest.read(sql,params);
	}
	
	
	//靈活的傳入語句和參數
	public static void read(String sql, Object[] params) throws SQLException{
		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		try {
			conn = JdbcUtils.getConnection();
			ps = conn.prepareStatement(sql);
			
			//可用於獲取關於 PreparedStatement 對象中每個參數標記的類型和屬性信息的對象
			ParameterMetaData pmd = ps.getParameterMetaData();
			int count = pmd.getParameterCount();
			
			for(int i=1; i<=count; i++){
				System.out.println(pmd.getParameterClassName(i));
				System.out.println(pmd.getParameterType(i));
				System.out.println(pmd.getParameterTypeName(i));
				ps.setObject(i, params[i-1]);
			}
			
			rs = ps.executeQuery();
			while(rs.next()){
				System.out.println(rs.getObject("name"));
				System.out.println(rs.getObject("birthday"));
			}
			
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			JdbcUtils.free(rs, ps, conn);
		}
	}
	
	
}