Integration

The Apache Jakarta POI project provides components for the access and generation of Excel documents. The POI HSSF API is used to generate Excel Workbooks and to add Excel spreadsheets to a workbook. An Excel spreadsheet consists of rows and cells. The layout and fonts of a spreadsheet are also set with the POI HSSF API.

A database table is often required to be presented in an Excel spreadsheet. Also, a developer's requirement could be to store an Excel spreadsheet in a database table. The Apache POI HSSF project is an API to create an Excel spreadsheet. The data in the Excel spreadsheet generated with the POI HSSF project may be static data in an XML document, or dynamically retrieved data from a database. Also, an Excel document may be converted to an XML document or be stored in a database. In this tutorial we will discuss the procedure to create an Excel spreadsheet from a MySQL database table in WebLogic Server. Subsequently, an Excel spreadsheet will be stored in a database table.

Preliminary Setup
The implementation of the POI HSSF project is provided in the org.apache.poi.hssf.usermodel package. The org.apache.poi.hssf.usermodel package classes are required in the Classpath to generate an Excel spreadsheet or to parse an Excel spreadsheet. Download the Apache POI library poi-bin-2.5.1-final-20040804.zip file and extract the zip file to an installation directory (http://jakarta.apache.org/poi/). Install WebLogic 8.1 Server. Download the MySQL database (www.mysql.com). Extract the MySQL zip file mysql-4.0.25-win32.zip to a directory. Install the MySQL database. Download the MySQL Connector/J JDBC driver (www.mysql.com/products/connector/j/). Extract the MySQL zip file mysql-connector-java-3.1.10.zip to a directory. Add the MySQL JDBC driver jar file, mysql-connector-java-3.1.10-bin.jar, to the <weblogic81>\samples\domains\examples\startExamplesServer script CLASSPATH variable.

Login to the MySQL database with the DOS command:

>mysql

Access the example database test with the command:

mysql>use test

Create an example database table in the MySQL database from which an Excel spreadsheet will be generated. The SQL script to create example table Catalog is shown in Listing 1.

Next, we will add the Apache POI .jar file to the WebLogic Server Classpath and create a JDBC datasource in the WebLogic Server to retrieve data for an Excel spreadsheet.

Add the poi-2.5.1-final-20040804.jar file to the CLASSPATH variable in the <weblogic81>\samples\domains\examples\startExamplesServer script. <weblogic81> is the directory in which the WebLogic Server is installed.

Next, create a JDBC connection with the MySQL database in WebLogic Server. Start the examples server with the script startExamplesServer. Access the administration console with the URL http://localhost:7001/console or with the Administration Console link in the WebLogic Server Examples index. In the administration console, right-click on the examples>Services>JDBC>Connection Pools node and select Configure a new JDBCConnectionPool. Specify the following connection properties to configure a JDBC connection pool:

• The database type: MySQL
• The JDBC driver: MySQL's Driver (Type 4)
• Database name: test
• Host name: localhost
• Port number: 3306
• Driver class name: com.mysql.jdbc.Driver
• Connection URL: jdbc:mysql://localhost:3306/test

Next, configure a JDBC datasource in the administration console. Right-click on the examples>Services>JDBC>DataSources node and select Configure a new JDBCTxDataSource. In the "Configure the data source" frame, specify a datasource name and a JNDI Name - MySqlDS, for example. In the "Connect to connection pool" frame select the Connection Pool previously configured with the MySQL database. In the "Target the datasource frame," select the examplesServer. A datasource gets configured with the MySQL database.

Generating an Excel Document with Apache POI
In this section we will generate an Excel spreadsheet from the example database table. First, create a JSP application to generate an Excel spreadsheet.

In the JSP an Excel spreadsheet will be created from a MySQL database table. The Apache POI HSSF API is used to generate an Excel spreadsheet. The Apache POI HSSF package has classes for the different components of an Excel spreadsheet. Some of the commonly used classes of the Apache POI HSSF package are listed in Table 1.

First, import the Apache POI HSSF package:

<%@ page import="org.apache.poi.hssf.usermodel.*, java.sql.*,
java.io.*,javax.naming.InitialContext"%>

Create an Excel stylesheet workbook:

HSSFWorkbook wb=new HSSFWorkbook();

Next, create an Excel spreadsheet:

HSSFSheet sheet1=wb.createSheet("sheet1");

The data for the stylesheet is retrieved from a MySQL database table. Obtain a JDBC connection from the database. The JDBC connection is obtained with the datasource JNDI MySqlDS.

InitialContext initialContext = new InitialContext();
javax.sql.DataSource ds = (javax.sql.DataSource)
initialContext.lookup("MySqlDS");
java.sql.Connection conn = ds.getConnection();

Create a java.sql.Statement and get a result set from the example table Catalog:

Statement stmt=conn.createStatement();
ResultSet resultSet=stmt.executeQuery("Select * from Catalog");

Create a header row for the Excel spreadsheet. The rows in an Excel spreadsheet are "0" based.

HSSFRow row=sheet1.createRow(0);

Set the header row cell values corresponding to the table columns. The row cells are also "0" based. For example, the value for the first cell in the row is set with the setCellValue method to CatalogId.

row.createCell((short)0).setCellValue("CatalogId");

To add rows to the spreadsheet, iterate over the result set and add a row for each of the table rows. Retrieve the column values from the ResultSet and set the values in the row cells.