The Template Design pattern in Spring

Let's see how to go about using the Template Design pattern in spring:

• Define the outline or skeleton of an algorithm

1. Leave the details for specific implementations until later.
2. Hide away large amounts of boilerplate code.

• Spring provides many template classes:
• JdbcTemplate
• JmsTemplate
• RestTemplate
• WebServiceTemplate
• Most hide low-level resource management

Let's look at the same code that we used earlier with Spring's JdbcTemplate and how it removes the boilerplate code.

Use JdbcTemplates to let your code the focus on the task:

    public Account getAccountById(long id) { 
      return jdbcTemplate.queryForObject( 
        "select id, name, amoount" + 
        "from account where id=?", 
         new RowMapper<Account>() { 
           public Account mapRow(ResultSet rs, 
            int rowNum) throws SQLException { 
              account = new Account(); 
              account.setId(rs.getLong("id")); 
              account.setName(rs.getString("name")); 
              account.setAmount(rs.getString("amount")); 
              return account; 
            } 
         }, 
      id); 
    } 

As you can see in the preceding code, this new version of getAccountById() is much simpler as compared to the boiler plate code, and here the method is focused on selecting an account from the database rather than creating a database connection, creating a statement, executing the query, handling the SQL exception, and finally closing the connection as well. With the template, you have to provide the SQL query and a RowMapper used for mapping the resulting set data to the domain object in the template's queryForObject() method. The template is responsible for doing everything for this operation, such as database connection and so on. It also hides a lot of boilerplate code behind the framework.

We have seen in this section how Spring attacks the complexities of Java development with the power of POJO-oriented development and patterns such as the DI pattern, the Aspect-using Proxy pattern, and the Template method design pattern.

In the next section, we will look at how to use a Spring container to create and manage the Spring beans in the application.