尝试从数据库向屏幕输出大约100个对象

Question

Web应用程序使用一个实体Bean（ejb 2.0），并有一个页面从数据库输出对象。我实现了实体中的所有方法，并检查了所有错误。我在数据库中有一个表，并尝试输出前100个对象（id和它们的名称）。但一百个物体需要20秒，速度很慢：（尝试了实体Bean的几个实现，结果是相同的。

private void loadRow（）引发SQLException、NamingException、Exception｛

    try {
    String selectStatement =
            "select parent_id, object_type_id, object_class_id, project_id, picture_id, name, description, attr_schema_id, order_number, source_object_id, versionn"+
            "from nc_objects where object_id = ?";
    Map results = (Map) JDBCExecutor.execute(selectStatement, Arrays.asList(new Object[]{new BigDecimal(objectId)}), new ResultSetHandler() {
        public Object onResultSet(ResultSet rs) throws Exception {
            Map results = new HashMap();
            if (rs.next()) {
                results.put("parent_id", checkedValue(rs, 1));
                results.put("object_type_id", checkedValue(rs, 2));
                results.put("object_class_id", checkedValue(rs, 3));
                results.put("project_id", checkedValue(rs, 4));
                results.put("picture_id", checkedValue(rs, 5));
                results.put("name", rs.getString(6));
                results.put("description", rs.getString(7));
                results.put("attr_schema_id", checkedValue(rs, 8));
                results.put("order_number", checkedValue(rs, 9));
                results.put("source_object_id", checkedValue(rs, 10));
                results.put("version", checkedValue(rs, 11));
            }
            return results;
        }
    });
    this.parentId = (BigInteger) results.get("parent_id");
    this.objectTypeId = (BigInteger) results.get("object_type_id");
    this.objectClassId = (BigInteger) results.get("object_class_id");
    this.projectId = (BigInteger) results.get("project_id");
    this.pictureId = (BigInteger) results.get("picture_id");
    this.name = (String) results.get("name");
    this.description = (String) results.get("description");        
    this.attrSchemaId = (BigInteger) results.get("attr_schema_id");
    this.orderNumber = (BigInteger) results.get("order_number");
    this.sourceObjectId = (BigInteger) results.get("source_object_id");
    this.version = (BigInteger) results.get("version");
    }
    catch(Exception ex){
        throw new Exception("My EXCEPTION; cannot load object_id = " + objectId, ex);
    }
    String selectStatement = "select object_id, attr_id, value, date_value, list_value_id, data "
            + " from nc_paramsn"
            + "where object_id = ?";
    params = (Map) JDBCExecutor.execute(selectStatement, Arrays.asList(new Object[]{new BigDecimal(objectId)}), new ResultSetHandler() {
        public Object onResultSet(ResultSet rs) throws Exception {
            Map results = new HashMap();
            while(rs.next()){
                if(rs.getString(3) != null)
                    results.put(checkedValue(rs, "attr_id"), rs.getString(3));
            }
            return results;
        }
    });
}

这是我的loadRow方法，它是从ejbLoad调用的。我不确定，但也许有麻烦？

Answer 1

EJB方法是以列表形式返回100个对象，还是每行调用100个？

EJB方法调用非常昂贵。尝试在一次往返中打包尽可能多的数据。

尝试对EJB调用中的代码进行计时（更好的是，对其进行分析）。你肯定JDBC调用是闪电般的快吗？

（我不是在问是什么让你在2012年使用EJB而不是更健康、更轻的体系结构；我希望它只是一个遗留系统。）