Using SQL in Template

Introduction

Jxls allows you to use SQL queries directly in Excel template to produce a collection that can be processed by Each-Command. The idea is to use an utility class that executes the SQL statement and converts the result set into a list of objects. Jxls ships with JdbcHelper class which can be used for this purpose.

JdbcHelper

To execute SQL queries in the template you can put an instance of JdbcHelper class into the context.
JdbcHelper object can be constructed by passing JDBC Connection instance to its constructor.

Connection conn = ... // get JDBC connection
JdbcHelper jdbcHelper = new JdbcHelper(conn);
context.putVar("jdbc", jdbcHelper);

Next you can refer to jdbc object in your Excel template to execute SQL queries for example

jx:each(items="jdbc.query('select * from employee where payment > ?', 2000)" var="employee" lastCell="C4")

In the above command we passed select * from employee where payment > ? SQL statement and also specified the substitution parameter (2000) to query method of the JdbcHelper instance.The query method has the following signature

  public List<Map<String, Object>> query(String sql, Object... params)

The method takes a query string and a list of substitution parameters to the query. During execution the method uses the Connection to execute the passed SQL using PreparedStatement.

Next it converts each row of the ResultSet to Map<String, Object> where keys of the map are the case insensitive column names and the values are the corresponding column values.

The created List<Map<String, Object>> is then processed by jx:each command in a regular way.

See SqlDemo Sample to see a working example of SQL usage in the template.