JDBC封装BaseDao

public class BaseDao {
    /**连接*/
    protected Connection con ;
    /**SQL语句执行对象*/
    protected PreparedStatement ps ;
    /**结果集*/
    protected ResultSet rs ;
    static {
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    
    public void setConnection() {
        try {
            con = DriverManager.getConnection(
                    "jdbc:mysql://localhost:6788/test?characterEncoding=utf-8", 
                    "root","xxxx");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    public void closeConnection() {
        try {
            if(rs != null) {
                rs.close();
            }
            if(ps != null) {
            }
            if(con != null) {
                con.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

/**
     * 更新数据
     * @param sql 语句
     * @param valueArray 占位符列表
     */
    public void updateDate(String sql,Object...valueArray) {
        this.setConnection();
        try {
            ps = con.prepareStatement(sql);
            for (int i = 0; i < valueArray.length; i++) {
                ps.setObject(i+1, valueArray[i]);
            }
            ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            this.closeConnection();
        }
    }

方法一:

public List find(String sql,Class c,Object...valueArray){
        List list = new ArrayList();
        this.setConnection();
        try {
            ps = con.prepareStatement(sql);
            if(valueArray != null) {
                for (int i = 0; i < valueArray.length; i++) {
                    ps.setObject(i+1, valueArray[i]);
                }
            }
            rs=ps.executeQuery();
            //得到结果集的审查对象
            ResultSetMetaData rm = rs.getMetaData();
            //得到查询结果的列数
            int num = rm.getColumnCount();
            while(rs.next()) {
                Object obj = c.newInstance();
                for (int i = 1; i <= num; i++) {
                    //得到对应列的列名
                    String columnName = rm.getColumnName(i);
                    Object columnObj = rs.getObject(columnName);
                    //根据列名，得到属性对象
                    Field f = c.getDeclaredField(columnName);
                    f.setAccessible(true);
                    //将对象指定的属性赋值为columnObj
                    f.set(obj, columnObj);
                }
                list.add(obj);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            this.closeConnection();
        }
        return list;
    }

方法二:

public List find(String sql,Class c,Object...valueArray){
        List list = new ArrayList();
        this.setConnection();
        try {
            ps = con.prepareStatement(sql);
            if(valueArray != null) {
                for (int i = 0; i < valueArray.length; i++) {
                    ps.setObject(i+1, valueArray[i]);
                }
            }
            //实体类属性列表
            Field[] f = c.getDeclaredFields();
            rs=ps.executeQuery();
            while(rs.next()) {
                Object obj = c.newInstance();
                for (int i = 0; i < f.length; i++) {
                    //去掉访问修饰符的检查
                    f[i].setAccessible(true);
                    String fname = f[i].getName();
                    try {
                        Object columnObj = rs.getObject(fname);
                        f[i].set(obj, columnObj);
                    } catch (Exception e) {
                        continue;
                    }
                }
                list.add(obj);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            this.closeConnection();
        }
        
        return list;
    }