根據今天所學，自己寫的JdbcUtil工具類。

其中update操作包含增刪改，使用事務處理

查詢操作分為兩種：

1、需要傳入sql語句（使用預編譯，用？佔位）、引數、需要包裝的實體類的class路徑；返回實體類的list（可以為單個）

2、傳入sql、引數。適用於查詢基本資料型別組成的list （可以為單個）

jdbcUtil.java程式碼：

import java.io.InputStream;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.Properties;

/**
 * Created by srg
 *
 * @date 2018/7/14
 */
public class JdbcUtil {

    private static String url = null;
    private static String username = null;
    private static String password = null;
    private static String driverClass = null;

    private static Connection conn = null;
    private static PreparedStatement pstm = null;
    private static ResultSet rs = null;

    static {
        try {
            Properties prop = new Properties();
            InputStream in = JdbcUtil.class.getResourceAsStream("/database.properties");
            prop.load(in);
            url = prop.getProperty("url");
            username = prop.getProperty("user");
            password = prop.getProperty("password");
            driverClass = prop.getProperty("driverClass");
            Class.forName(driverClass);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 獲取資料庫連結
     * @return
     */
    public static Connection getConnection(){
        Connection conn = null;
        try {
            conn = DriverManager.getConnection(url, username, password);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return conn;
    }

    /**
     * ResultSet的關閉
     */
    public static void close(Connection conn, PreparedStatement pstm, ResultSet rs){
        if(conn != null){
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if(pstm != null){
            try {
                pstm.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if(rs != null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * 執行插入操作
     * @param sql       sql語句
     * @param param     需要的引數
     * @return
     */
    public static boolean executeUpdate(String sql, ArrayList param){
        boolean flag = false;
        conn = JdbcUtil.getConnection();
        try {
            pstm = conn.prepareStatement(sql);
            for (int i = 0;i < param.size();i++){
                pstm.setObject(i + 1, param.get(i));
            }
            pstm.executeUpdate();
            flag = true;
        } catch (SQLException e) {
            e.printStackTrace();
            return flag;
        } finally {
            JdbcUtil.close(conn, pstm, rs);
        }
        return flag;
    }

    /**
     * 執行更新批處理操作，使用事務處理，成功則提交事務，不成功則回滾
     * @param sql
     * @param param
     * @return
     */
    public static boolean executeUpdate(String[] sql, ArrayList<ArrayList> param){
        boolean flag = false;
        conn = JdbcUtil.getConnection();
        try {
            //設定為手動提交
            conn.setAutoCommit(false);

            for(int i = 0;i < sql.length;i++){
                pstm = conn.prepareStatement(sql[i]);
                for (int j = 0;j < param.size();j++){
                    pstm.setObject(j + 1, param.get(i).get(j));
                }
                pstm.addBatch();
            }
            pstm.executeBatch();
            //如果執行成功了，就提交
            conn.commit();
            flag = true;
        } catch (SQLException e) {
            e.printStackTrace();
            try {
                //不成功，回滾
                conn.rollback();
            } catch (SQLException e1) {
                e1.printStackTrace();
            }
            return flag;
        } finally {
            JdbcUtil.close(conn, pstm, rs);
        }
        return flag;
    }

    /**
     * 執行查詢操作
     * @param sql       sql語句
     * @param param     需要的引數
     * @param classPath 根據傳入的path,反射為實體類,封裝到list中
     * @return          將封裝好的list返回
     */
    public static ArrayList executeQuery(String sql, ArrayList param, String classPath){
        ArrayList result = new ArrayList();
        conn = JdbcUtil.getConnection();
        try {
            pstm = conn.prepareStatement(sql);
            for (int i = 0;i < param.size();i++){
                pstm.setObject(i + 1, param.get(i));
            }
            rs = pstm.executeQuery();

            Class c = Class.forName(classPath);
            while(rs.next()){
                Object obj = c.newInstance();
                Field[] fields = c.getDeclaredFields();
                for (Field field : fields){
                    String ftype = field.getType().getSimpleName();
                    String fname = field.getName();

                    //如果不存在，繼續
                    if(!isExists(rs, fname)){
                        continue;
                    }

                    Object value = null;
                    if("string".equalsIgnoreCase(ftype)){
                        value = rs.getString(fname);
                    } else if("int".equalsIgnoreCase(ftype) || "integer".equalsIgnoreCase(ftype)){
                        value = rs.getInt(fname);
                    } else if("float".equalsIgnoreCase(ftype)){
                        value = rs.getFloat(fname);
                    } else if("double".equalsIgnoreCase(ftype)){
                        value = rs.getDouble(fname);
                    } else if("boolean".equalsIgnoreCase(ftype)){
                        value = rs.getBoolean(fname);
                    } else if("date".equalsIgnoreCase(ftype)){
                        value = rs.getTimestamp(fname);
                    }

                    //使用setXXX方法
                    fname = fname.substring(0,1).toUpperCase() + fname.substring(1);
                    String mName = "set" + fname;
                    Method m = c.getDeclaredMethod(mName, field.getType());
                    m.invoke(obj, value);
                }
                //將封裝好的資料依次加入result
                result.add(obj);
            }
        } catch (Exception e) {
            e.printStackTrace();
            result = new ArrayList();
            return result;
        } finally {
            JdbcUtil.close(conn, pstm, rs);
        }
        return result;
    }

    /**
     * 查詢單個數據
     * @param sql       sql語句
     * @param param     需要的引數
     * @return          返回值為基本型別或者String的list
     */
    public static ArrayList executeQuery(String sql, ArrayList param){
        ArrayList result = new ArrayList();
        conn = JdbcUtil.getConnection();
        try{
            pstm = conn.prepareStatement(sql);
            for (int i = 0;i < param.size();i++){
                pstm.setObject(i + 1, param.get(i));
            }
            rs = pstm.executeQuery();

            while (rs.next()){
                Object object = rs.getObject(1);
                result.add(object);
            }
        } catch (Exception e){
            e.printStackTrace();
            return new ArrayList();
        } finally {
            JdbcUtil.close(conn, pstm, rs);
        }
        return result;
    }

    public static boolean isExists(ResultSet rs,String column)
    {
        try {
            rs.findColumn(column);
        } catch (SQLException e) {
            return false;
        }
        return true;
    }
}
 

其中database.properties中儲存資料庫的資訊

url=jdbc:mysql://localhost:3306/gs
user=root
password=
driverClass=com.mysql.jdbc.Driver

由於使用到了反射，所以bean（實體類）裡面的set get函式必須標準命名。

例如:

user.java(僅作為例子）

public class UserBean {
    
    private String username;
    private String password;

    public UserBean() {
    }

    public UserBean(String username, String password) {
        this.username = username;
        this.password = password;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}
 

使用例項：（我還沒驗證。。。瞎寫一下）

public User login(String username, String password){
        String sql = "select * from user where username=? and password=?";

        ArrayList<String> param = new ArrayList<>();
        param.add(username);
        param.add(password);

        String path = "com.gs.bean.UserBean";
        ArrayList userList = JdbcUtil.executeQuery(sql,param,path);
        User user = new User();
        if(userList.size() > 0) {
            user = (User) userList.get(0);
        }
        return user;
    }