看了以前寫的代碼，對就是下面這個

手把手封裝數據層之DataUtil數據庫操作的封裝

覺得以前寫的代碼好爛啊！！！，重新理了一下思路，寫得更規範和簡練，應該效率也會高很多，用了一下下午寫的連接池（半廢品。。。）

瞎j8封裝第二版之數據庫連接池

下面直接上代碼，代碼很好理解，就是用了簡單的反射，註解的部分我都寫了註釋

package jdbc;

import util.StringUtil;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
 
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class DataUtil {


    public static int excuteUpdate(String sql, Object... objects) {
        Connection connection = ConnectionPool.getInstance().getCurrentConnection();
        PreparedStatement preparedStatement = null
 
;
        try {
            preparedStatement = getStateMent(connection, sql, objects);
            return preparedStatement.executeUpdate(); //執行sql並返回結果
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            if (preparedStatement != null) {
                
 
try {
                    preparedStatement.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }

        }
        return 0;
    }


    /**
     * 查詢單挑記錄
     *
     * @param sql  查詢語句
     * @param clazz 返回對象的class
     * @param objects 需要的參數，必須跟sql占位符的位置一一對應
     * @param <T>   泛型返回
     * @return      返回單個對象
     */
    public static <T> T queryForObject(String sql, Class<T> clazz, Object... objects) {
        Connection connection = ConnectionPool.getInstance().getCurrentConnection();
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        T object = null;
        try {
            preparedStatement = getStateMent(connection, sql, objects);
            resultSet = getResultSet(preparedStatement);
            if (resultSet.next()) {
                object = invokeObject(resultSet, clazz);
            }

        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        } finally {
            close(preparedStatement, resultSet); //記得關閉
        }
        return object;
    }

    /**
     *查詢多條記錄
     *
     * @param sql  查詢語句
     * @param clazz 返回對象的class
     * @param objects 需要的參數，必須跟sql占位符的位置一一對應
     * @param <T>   泛型返回
     *
     * @return list
     */
    public static <T> List<T> queryForList(String sql, Class<T> clazz, Object... objects) {
        Connection connection = ConnectionPool.getInstance().getCurrentConnection();
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        List<T> list = new ArrayList<T>();
        try {
            preparedStatement = getStateMent(connection, sql, objects);
            resultSet = getResultSet(preparedStatement);
            while (resultSet.next()) {
                list.add(invokeObject(resultSet, clazz));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        } finally {
            close(preparedStatement, resultSet);
        }

        return list.size() > 0 ? list : null;

    }


    private static void close(PreparedStatement preparedStatement, ResultSet resultSet) {
        try {
            if (preparedStatement != null) {
                preparedStatement.close();
                resultSet.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    private static <T> T invokeObject(ResultSet resultSet, Class<T> clazz) throws IllegalAccessException, InstantiationException,
            SQLException, NoSuchFieldException, NoSuchMethodException, InvocationTargetException {
        T object = clazz.newInstance();
        ResultSetMetaData metaData = resultSet.getMetaData();
        for (int i = 0, count = metaData.getColumnCount(); i < count; i++) {
            String columnName = metaData.getColumnName(i + 1);     //數據庫返回結果的列名
            String fieldName = StringUtil.camelName(columnName); //去掉列名中的下劃線“_”並轉為駝峰命名
            Field field = clazz.getDeclaredField(fieldName);            //根據字段名獲取field
            String methName = setMethodName(fieldName);         //拼set方法名
            Class type = field.getType();                       //獲取字段類型
            Method setMethod = clazz.getDeclaredMethod(methName, field.getType());
            Object value = resultSet.getObject(i + 1);            //獲取字段值
            setMethod.invoke(object, type.cast(value));       //強轉並且賦值
        }
        return object;
    }

    private static PreparedStatement getStateMent(Connection connection, String sql, Object... objects) throws SQLException {
        if (connection == null) {
            return null;
        }
        PreparedStatement preparedStatement = connection.prepareStatement(sql);
        for (int i = 0, len = objects.length; i < len; i++) {
            preparedStatement.setObject(i + 1, objects[i]);  //給sql每個？占位符填上數據
        }
        return preparedStatement;
    }

    private static ResultSet getResultSet(PreparedStatement statement) throws SQLException {
        if (statement == null) {
            return null;
        } else {
            return statement.executeQuery();
        }
    }

    private static String setMethodName(String str) {
        return "set" + StringUtil.firstUpperCase(str);
    }

}

用到了幾個簡單的字符串處理方法

package util;

public class StringUtil {

    /**
     * 轉為駝峰命名
     * @param str
     * @return string
     */
    public static String camelName(String str) {
        if (!isEmpty(str)) {
            StringBuilder stringBuilder = new StringBuilder();
            for (int i = 0, len = str.length(); i < len; i++) {
                if (str.charAt(i) == ‘_‘) {
                    while (str.charAt(i + 1) == ‘_‘) {
                        i++;
                    }
                    stringBuilder.append(("" + str.charAt(++i)).toUpperCase());
                } else {
                    stringBuilder.append(str.charAt(i));
                }
            }
            return stringBuilder.toString();
        }
        return str;
    }

    /**
     * 判斷是否為空串
     * 
     * @param str
     * @return
     */
    public static boolean isBlank(String str) {
        if (str != null && str.length() > 0) {
            for (int i = 0, len = str.length(); i < len; i++) {
                if (!Character.isSpaceChar(str.charAt(i))) {
                    return false;
                }
            }
        }
        return true;
    }

    /**
     * 判斷是否為空串 ？！！！ 我怎麽又寫了個一樣的方法？！！！
     * @param str
     * @return
     */
    public static boolean isEmpty(String str) {
        return str == null || str.length() == 0;
    }


    /**
     * 將第一個字母替換為大寫
     * @param str
     * @return
     */
    public static String firstUpperCase(String str) {
        return str.substring(0, 1).toUpperCase() + str.substring(1, str.length());
    }
    
}

下面開始是測試了

首先數據庫

然後測試類，跟表結構對應的

package po;

import java.util.Date;

public class User {

    private Integer id;
    private Integer age;
    private String name;
    private Double score;
    private Date createTime;
    private Date updateTime;

   //set、get 方法均省略了，但是這個是必須的
｝

測試代碼

import java.util.List;

public class Test {

    public static void main(String[] args) {
        String sql = "select * from t_user";
        List<User> list = DataUtil.queryForList(sql,User.class);
        System.out.println("查詢多條記錄：" + list);
        System.out.println("******************************************************************");


        sql = "select * from t_user where id = ?";
        User user = DataUtil.queryForObject(sql,User.class,1);
        System.out.println("查詢單條記錄：" + user);
        System.out.println("******************************************************************");


        sql = "insert into t_user(name,score,create_time,update_time) values(?,?,now(),now())";
        int t = DataUtil.excuteUpdate(sql,"大牛",66.66);
        System.out.println("執行插入操作結果："+t);

    }
}

測試結果

太晚了，先到這了，有空把我的mybatis和ioc容器也瞎j8重寫一下

轉載請註明出處：

大王讓我寫代碼 00:12:24

瞎j8封裝第二版之數據層的封裝