第二十九章 参数的元数据信息

灵活的传入sql语句，和sql语句的参数

报错：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);}//灵活的传入语句和参数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);//可用于获取关于 PreparedStatement 对象中每个参数标记的类型和属性信息的对象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);}}}