是用JDBC从数据库中获取数据并以java对象返回

朱雀 2022-08-27 04:51 160阅读 0赞

/**
    	 * 
    	 * @param c
    	 *            for example Person.class
    	 * @param primaryKeys
    	 *            primaryKeys为主键,参数顺序和表中保持一致 如果id， name 为主键 类名为Person 则 getEntity(Person.class,1,"name")
    	 * @return
    	 */
    	public static Object getEntity(Class c, Object... primaryKeys) {
    		PreparedStatement ps = null;
    		ResultSet rs = null;
    		DatabaseMetaData dmd = null;
    		Object obj = null;// 要返回的对象
    		String tableName = c.getSimpleName().toLowerCase();// person 表的名字
    		List primaryKeyNameList = new ArrayList();
    		Field[] fields = c.getFields();// 获取所有的属性
    		StringBuilder sql = new StringBuilder("select * from " + tableName
    				+ " where ");
    		try {
    			obj = c.newInstance();
    			dmd = getConnection().getMetaData();
    			rs = dmd.getPrimaryKeys(null, null, tableName);
    			while (rs.next()) {
    				sql.append(rs.getObject(4) + "=?");
    				sql.append(" and ");
    				primaryKeyNameList.add(rs.getObject(4));// 将从表中获取的 主键字段存到 list中， 主键位于表中第几列=rs.getString(5)
    			}
    			sql.delete(sql.length() - 4, sql.length());
    			ps = (PreparedStatement) getConnection().prepareStatement(
    					sql.toString());
    			for (int l = 0; l < primaryKeyNameList.size(); l++) {
    				ps.setObject(l + 1, primaryKeys[l]);
    			}
    			rs = ps.executeQuery();
    			System.out.println(ps.toString().split(":")[1]);
    			if (rs.next()) {
    				for (int k = 0; k < fields.length; k++) {
    					fields[k].set(obj, rs.getObject(k + 1));
    				}
    			}
    			rs.close();
    			ps.close();
    			rs=null;
    			ps=null;
    		} catch (Exception e) {
    			e.printStackTrace();
    		} finally {
    			
    		}
    		return obj;
    	}