April 3, 2014

How does Java process non-database structured data

In Java, implementing via SQL is a well-developed practice for database computing. However, the structured data is not only stored in the database, but also in the text, Excel, and XML files. Considering this, how to compute appropriately regarding the structured data from non-database files? This article raises 3 solutions for your reference: implement via Java API, convert to database computation, and adopt the common data computation layers.

Implement via Java API. This is the most straightforward method. Programmers will benefit from Java API in controlling every computational step meticulously, monitoring the computed result in each step intuitively, and debugging conveniently. Needless to say, no learning cost is also an additional advantage of Java API.

Thanks to the well-developed API for retrieving and writing-back data to Txt, Excel, and XML files, Java has enough technical strength to offer the full support for such computation, in particular the simple computational goals.

However, this method requires great workload and quite inconvenient.

For example, since the common data algorithms have not implemented in Java, programmers will have to spend great time and efforts to implement all the ins and outs manually by aggregating, filtering, grouping, and sorting and some other common actions.

For another example of data storage and detail data retrieval through Java API, programmers will have to combine every data and 2D table with List/map and other objects, and then compute in nested loops at multi-levels. Moreover, such computation usually involves the set operations and relational computations on massive data, as well as the computations between objects and object properties. It takes great efforts to implement the underlying logics and even greater workload in handling the complex ordered computation.

In order to reduce the programing workload, programmers always prefer leveraging the existing algorithms to implementing all specifics by themselves. In view of this, the second choice below would be a better choice:
Convert to database computationThis is the most conservative method. Concretely speaking, it is to import the non-database data to the database via the common ETL tools like DataStage, DTS, Informatica, and Kettle. The advantages of this practice include the high computational efficiency, steadfast running, and less workload for Java programmers. It fits for the scenarios of great data volume, high performance demand, and medium-level computational complexity. These advantages are evident for the mixed computation on the database and the non-database files in particular.

The main drawback of this method is the great workload in the early stage of ETL and the great maintenance difficulty. First, since the non-database data cannot be used directly without field-splitting, merging, and judging, programmers have to write a great many of Perl/JS scripts to clean and re-organize the data. Second, the data is usually updatable, so the scripting must handle the changing incremental update issues. The data from various data sources can hardly be compatible with a normal form. So, the data is unusable before the level 2 or even the level 3 ETL process. Third, scheduling is also a problem when there are lots of tables – which table must be uploaded first? Which one is the second to upload? What’s the interval? In facts, the huge workload of ETL is always beyond our expectation, and it is always quite tough to evade project risk. Plus, the real-time performance of ETL is poor owing to the regular transit of the database.

In some operating environments, there is probably no database service at all for the sake of security or performance. For another example, if most data is saved in the TXT/XML/Excel and no database involved, then the existence value of ETL gets void. What can we do? Let’s try the 3rdmethod:
The common data computing layer is typified by the esProc and R. The data computational layer is a layer in-between the data persistence layer and the application layer. This layer is responsible for computing the data from data persistence layer uniformly and returning the computed result to the application layer. The data computation layer of Java is mainly used to reduce the coupling between the application layer and the data persistence layer, and alleviate the computational pressure on them.
The common data computational layer offers the direct support for various data sources - not only the database, but also the non-database data sources. By taking the advantage, programmers can access to various data sources directly, free from such things as real-time problems. In addition, programmers are allowed to implement the interactive computation between various data sources conveniently, for example, the computations between DB2 and Oracle, and MYSQL and Excel. In the past, such access is by no means easy to implement.

The versatile data computational layers are usually more professional on structured data, for example, it supports the generic, explicit set, and ordered array. So, the complex computational goals, which are tough jobs for ETL/SQL and other conventional tools, can be solved with this layer easily.

The drawback of such method mainly lies in the performance. The common data computation layer is of the full memory computation, so the size of memory determines the upper limit of the data volumes to handle. But both esProc and R support the Hadoop directly so that their users can handle the big data in the distributed environment.

The main difference between esProc and R is that esProc supports the direct JDBC output and convenient integrating with Java codes. In addition, esProc IDE is much easier to use, with the support for the true debugging, and scripts in grid, and cell name for direct referencing the computed result. R does not provide such advantages, nor support for JDBC, and thus a bit complex for R users to integrate. However, R supports the correlation analyses and other model analyses. R programmers do not have to implement all specifics to generate the computed result directly. R also supports the Txt/ Excel / XML files and other lots of more non-database data sources. By comparison, esProc only supports 2 of them. The last but not the least advantage of R is that the low-end edition of R supports the open source to the full.

The above is the comparison between these three methods, and you can choose the right one based on your project characteristics.

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