JDBC查询、插入数据库

public class DB_Util {
    public static String DRIVERS = "";
    public static String URL = "";
    public static String USER = "";
    public static String PASSWORD = "";
    static{
        Properties prop = new Properties();
        InputStream in = Thread.currentThread().getContextClassLoader().getResourceAsStream("db.properties");
        try {
            prop.load(in);
            DRIVERS = prop.getProperty("driver");
            URL = prop.getProperty("url");
            USER = prop.getProperty("user");
            PASSWORD = prop.getProperty("password");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

#connection
#MySQL
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/test
user=Gikin_db
password=tiger

#oracle
#driver=oracle.jdbc.driver.OracleDriver
#url=jdbc:oracle:thin:@//loaclhost:1521/orcl
#user=SCOTT
#password=tiger

public static Connection openDB() {
        Connection con = null;
        try {
            Class.forName(DB_Util.DRIVERS);
            con = DriverManager.getConnection(DB_Util.URL, DB_Util.USER, DB_Util.PASSWORD);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return con;
    }
    public static void closeDB(Connection con, Statement stmt, ResultSet rs) {

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

    public static void closeDB(Connection con, Statement stmt, ResultSet rs) {

        try {
            if (rs != null) {
                rs.close();
            }
            if (stmt != null) {
                stmt.close();
            }
            if (con != null) {
                con.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            rs = null;
            stmt = null;
            con = null;
        }
    }
    public static void closeDB(Connection con, Statement stmt) {

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

public static void main(String[] args) {
        //构造查询条件sql语句
        String sql = "where deptno = ?";
        //Object[]中存储的是要查询的条件,同时反射获得实体
        List<?> list = SELECT.getROW(sql,new Object[] {20}, EMP.class);
        for (Object object : list) {
            System.out.println(object);
        }
    }

public static String creatSetter(String colName) {
        //利用传入的属性名拼接set方法名
        String setMethod = "set" + colName.substring(0, 1) + colName.substring(1).toLowerCase();
        return setMethod;
    }

    public static List<?> getROW(String sql, Object[] obj, Class<?> clazz) {
        
        List<Object> list = new ArrayList<Object>();
        //通过实体获得类名,同时也是表名
        String clazzName = clazz.getSimpleName();
        //拼接sql语句
        String selectSQL = "select * from " + clazzName + " " + sql;
        
        Connection con = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            //连接数据库
            con = DBHelp.openDB();
            //将sql存入PreparedStatement对象准备发送到数据库
            ps = con.prepareStatement(selectSQL);
            //绑定Object[]中的条件到ps中的sql上的？占位符
            for (int i = 0; i < obj.length; i++) {
                ps.setObject(i + 1, obj[i]);
            }
            //执行sql语句，返回一个结果集
            rs = ps.executeQuery();

            while (rs.next()) {
                //获得实例
                Object instance = clazz.newInstance();
                //获得结果集中的每列的数量,类型和属性
                ResultSetMetaData metaData = rs.getMetaData();
                
                for (int i = 0; i < metaData.getColumnCount(); i++) {
                    //获得列名即字段名
                    String colName = metaData.getColumnName(i + 1);
                    //获得结果集中每列对应的值
                    Object colValue = rs.getObject(i + 1);
                    //获得类中的属性
                    Field field = clazz.getDeclaredField(colName.toLowerCase());
                    //获得类属性对应的set方法
                    Method method = clazz.getDeclaredMethod(creatSetter(colName), field.getType());
                    //Mysql中的数据类型需要转换才能赋入对象
                    if (colValue instanceof Number) {
                        if (field.getType().getName().equals("int")
                                || field.getType().getName().equals("java.lang.Integer")) {
                            method.invoke(instance, ((Number) colValue).intValue());
                        } else if (field.getType().getName().equals("float")
                                || field.getType().getName().equals("java.lang.Float")) {
                            method.invoke(instance, ((Number) colValue).floatValue());
                        } else if (field.getType().getName().equals("double")
                                || field.getType().getName().equals("java.lang.Double")) {
                            method.invoke(instance, ((Number) colValue).doubleValue());
                        }
                    } else if (colValue == null) {
                        method.invoke(instance, 0.0);
                    } else {
                        method.invoke(instance, colValue);
                    }
                }
                list.add(instance);
            }

        } catch (Exception e) {
            e.printStackTrace();
        }  finally {
            DBHelp.closeDB(con, ps, rs);
        }

        return list;
    }

//构造插入的对象
        EMP emp = new EMP(1111, "cai111", "singer", 7788,new Date(), 5600, 10.0, 10);
        int isSuccess = INSERT.insert(emp);
        System.out.println( isSuccess==1 ? "添加成功!" : "添加失败!");

    public static int insert(Object obj) {
        int isSuccess = 0;
        Connection conn = DBHelp.openDB();
        PreparedStatement ps = null;
        //拼接sql语句,属性使用＂？＂占位符等待绑定
        String SQL = "insert into " + obj.getClass().getSimpleName() + " values(?,?,?,?,?,?,?,?)";
//        System.out.println(SQL);
        try {
            ps = conn.prepareStatement(SQL);
            Field[] fields = obj.getClass().getDeclaredFields();
            //依次绑定属性到占位符上
            for (int i = 0; i < fields.length; i++) {
                //java的Date需要转换为sql的Date才能添加到数据库
                if (setField(obj, fields[i]) instanceof Date) {
                    Date date = (Date) setField(obj, fields[i]);
                    //所有的数据类型均继承自Object,所以直接使用Object避免类型不匹配异常
                    ps.setObject(i+1,new java.sql.Date(date.getTime()));
                } else {
                    ps.setObject(i+1,setField(obj, fields[i]));
                }
            }
            //执行sql语句，返回一个int表示是否操作成功
            isSuccess = ps.executeUpdate();
            //提交
            conn.commit();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            DBHelp.closeDB(conn, ps);
        }
        
        return isSuccess;
    }
    
    public static Object setField(Object obj,Field field) {
        String name = field.getName();
        String methodName = "get" + name.substring(0,1).toUpperCase() + name.substring(1,name.length());
        Object setField = null;
        try {
            Method method = obj.getClass().getMethod(methodName);
            setField = method.invoke(obj);
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (SecurityException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        } 
        return setField;
    }
}