JDBC框架

public class JdbcUtils {
    
    private static DataSource ds = null;
    static{
        try{
            InputStream in = JdbcUtils.class.getClassLoader().getResourceAsStream("dbcpconfig.properties");
            Properties prop = new Properties();
            prop.load(in);
            BasicDataSourceFactory factory = new BasicDataSourceFactory();
            ds = factory.createDataSource(prop);
        }catch (Exception e) {
            throw new ExceptionInInitializerError(e);
        }
    }

    public static Connection getConnection() throws SQLException{
        return ds.getConnection();
    }
    
    
    public static void release(Connection conn,Statement st,ResultSet rs){
        
        if(rs!=null){
            try{
                rs.close();   //throw new 
            }catch (Exception e) {
                e.printStackTrace();
            }
            rs = null;
        }
        if(st!=null){
            try{
                st.close();
            }catch (Exception e) {
                e.printStackTrace();
            }
            st = null;
        }
        if(conn!=null){
            try{
                conn.close();
            }catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
    
    //String sql = "insert into account(id,name,money) values(?,?,?)"   object[]{1,"aaa","10000"};
    public static void update(String sql,Object params[]) throws SQLException{
        Connection conn = null;
        PreparedStatement st = null;
        ResultSet rs = null;
        try{
            conn = getConnection();
            st = conn.prepareStatement(sql);
            for(int i=0;i<params.length;i++){
                st.setObject(i+1,params[i]);
            }
            st.executeUpdate();
        }finally{
            release(conn, st, rs);
        }
    }
    
    //
    public static Object query(String sql,Object params[],ResultSetHandler handler) throws SQLException{
        Connection conn = null;
        PreparedStatement st = null;
        ResultSet rs = null;
        try{
            conn = getConnection();
            st = conn.prepareStatement(sql);
            for(int i=0;i<params.length;i++){
                st.setObject(i+1,params[i]);
            }
            rs = st.executeQuery();
            return handler.handler(rs);
        }finally{
            release(conn, st, rs);
        }
    }
}    

interface ResultSetHandler{
    public Object handler(ResultSet rs);
}


class BeanHandler implements ResultSetHandler{

    private Class clazz;
    public BeanHandler(Class clazz){
        this.clazz = clazz;
    }
    
    public Object handler(ResultSet rs) {
        try{
            if(!rs.next()){
                return null;
            }
            
            //创建封装结果集的bean
            Object bean = clazz.newInstance();
            
            //得到结果集的元数据，以获取结果集的信息
            ResultSetMetaData meta = rs.getMetaData();
            int count = meta.getColumnCount();
            for(int i=0;i<count;i++){
                String name = meta.getColumnName(i+1);   //获取到结果集每列的列名  id
                Object value = rs.getObject(name);     //1
                
                //反射出bean上与列名相应的属性
                Field f = bean.getClass().getDeclaredField(name);
                f.setAccessible(true);
                f.set(bean, value);
            }
        
            return bean;
        
        }catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

class BeanListHandler implements ResultSetHandler{

    private Class clazz;
    public BeanListHandler(Class clazz){
        this.clazz = clazz;
    }
    public Object handler(ResultSet rs) {
        List list = new ArrayList();
        try{
            while(rs.next()){
                Object bean = clazz.newInstance();
                ResultSetMetaData  meta = rs.getMetaData();
                int count = meta.getColumnCount();
                for(int i=0;i<count;i++){
                    String name = meta.getColumnName(i+1);
                    Object value = rs.getObject(name);
                    
                    Field f = bean.getClass().getDeclaredField(name);
                    f.setAccessible(true);
                    f.set(bean, value);
                }
                list.add(bean);
            }
        }catch (Exception e) {
            throw new RuntimeException(e);
        }
        return list;
        
    }
    
    
    
}