uangsl / sqlbuilder

SQL Builder Library for Java

SQL Builder Utilities

This package contains a number of utility classes to simplify working with SQL.

Maven

Add the following dependency to your POM:

<dependency>
  <groupId>ca.krasnay</groupId>
  <artifactId>sqlbuilder</artifactId>
  <version>1.0</version>
</dependency>

SQL Builder depends on slf4j and Spring JDBC, so be sure to add the desired versions of these to your <dependencyManagement> section.

Builders

Builders simplify the creation of SQL strings. They know a little bit about SQL syntax, and make the creation of dynamic SQL a little nicer in Java. Like Java's StringBuilder, they use chainable calls. Here's an example of using SelectBuilder.

new SelectBuilder()
.column("name")
.column("age")
.from("Employee")
.where("dept = 'engineering'")
.where("salary > 100000")
.toString();

This produces the SQL string select name, age from Employee where dept = 'engineering' and salary > 100000. Note how SelectBuilder knows to join the columns with a comma and to join the where clauses with and.

For more info, see http://john.krasnay.ca/2010/02/15/building-sql-in-java.html

ParameterizedPreparedStatementCreator

Spring has a powerful abstraction known as JdbcTemplate that makes working with JDBC bearable. JdbcTemplate takes care of the proper allocation and disposal of JDBC connections from a DataSource. It never returns a Connection; instead, connection objects are passed to callbacks provided by the caller. Once such callback, the PreparedStatementCreator, is used to create a prepared statement given a connection.

In a typical PreparedStatementCreator, one creates SQL with substitutable parameters indicated by question marks, then sets the parameter values by index. Keeping track of these indexes can be challenging when working with dynamic SQL. To simplify this, ParamerizedPreparedStatementCreator uses named parameters. Here's an example:

PreparedStatementCreator psc =
    new ParameterizedPreparedStatementCreator()
    .setSql("update Employee set name = :name where id = :id")
    .setParameter("name", "Bob")
    .setParameter("id", 42);

new JdbcTemplate(dataSource).update(psc);

Creators

Each builder class has a corresponding Creator class that combines a builder and a ParameterizedPreparedStatmentCreator.

PreparedStatementCreator psc =
    new UpdateCreator("Employee")
    .setValue("name", "Bob")
    .whereEquals("id", 42);

new JdbcTemplate(dataSource).update(psc);

Creators don't add much functionality themselves, but they make working with builders and ParameterizedPreparedStatementCreators a little easier (plus you don't have to keep typing that ridiculously large class name!).