有谁能给个封装结果集的例子mysql的并注解一下,学习java的

发布网友发布时间：2022-05-01 15:37

共2个回答

热心网友时间：2022-05-01 17:07

package com.golden.;

import java.lang.reflect.Method;
import java.sql.ResultSet;

/**
* 行映射器
*
* @author pine
*
*/
public class RowMapper {

    /**
     * 将结果集中一行映射为对象
     * @param resultSet
     * @param clazz
     * @return T
     */
    public <T> T mappingRow(ResultSet resultSet, Class<T> clazz) {
        class StringHelper{
            /**
             * 首字母大写
             * @param str
             * @return String
             */
            private String toUpperCase(String str){
                String firstLetter = str.substring(0, 1).toUpperCase();
                if (str.length()==1) {
                    return firstLetter;
                }
                return firstLetter.concat(str.substring(1));
            }

            /**
             * 获取方法名
             * @param strs
             * @return String
             */
            private String getMethodName(String[] strs){
                StringBuffer methodName = new StringBuffer("set");
                for (String temp : strs) {
                    if (temp.equals("")) {
                        continue;
                    }
                    methodName.append(this.toUpperCase(temp));
                }
                return methodName.toString();
            }

            /**
             * 获取方法名
             * @param field
             * @return String
             */
            public String getMethodName(String field){
                return this.getMethodName(field.split("_"));
            }
        }
        StringHelper helper = new StringHelper();
        try {
            T t = clazz.newInstance();
            int columnCount = resultSet.getMetaData().getColumnCount();
            Method[] methods = clazz.getMethods();
            outer:for (int i = 0; i < columnCount; i++) {
                String field = resultSet.getMetaData().getColumnLabel(i+1);
                String methodName = helper.getMethodName(field);
                for (Method method : methods) {
                    if (method.getName().equals(methodName)) {
                        method.invoke(t, resultSet.getObject(i+1));
                        continue outer;
                    }
                }
            }
            return t;
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }
    }
}

使用的时候：

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import com.golden..BankDao;
import com.golden..RowMapper;
import com.golden.util.DbcpUtils;
import com.golden.vo.Bank;
//继承RowMapper
public class BankDaoImpl extends  RowMapper implements BankDao {

    public List<Bank> findBanks(String query, int start, int limit) {
        Connection connection = DbcpUtils.getConnection();
        String sql = "select * from bank  t where (t.bank_no like concat('%',?,'%') or t.bank_name like concat('%',?,'%')) order  by t.id asc  limit ?,?;";
        DbcpUtils.printlnSQL(sql);
        PreparedStatement preparedStatement =null;
        ResultSet resultSet = null;
        try {
            preparedStatement  = connection.prepareStatement(sql);
            preparedStatement.setString(1, query);
            preparedStatement.setString(2, query);
            preparedStatement.setInt(3, start);
            preparedStatement.setInt(4,limit);
            resultSet =preparedStatement.executeQuery();
            List<Bank> banks = new ArrayList<Bank>();
            while (resultSet.next()) {
                banks.add(this.mappingRow(resultSet, Bank.class));//调用封装方法
            }
            return banks;
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }finally{
           DbcpUtils.closeConnection(connection, preparedStatement, resultSet);
        }
    }

}

热心网友时间：2022-05-01 18:25

select * from (
(SELECT uid,je,starttime,stoptime,1 as type from (SELECT id from members WHERE referer='4') as m JOIN (SELECT uid,je,starttime,stoptime from `cz` WHERE `status`>0) as c on c.uid=m.id)
union
(SELECT uid,je,starttime,stoptime,2 as type from (SELECT id from members WHERE referer='4') as m JOIN (SELECT uid,je,starttime,stoptime from `withdrawh` WHERE `state`=1) as w on w.uid=m.id)
) order by starttime