2V0-72.22 Exam Dumps - Spring Professional Develop

https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/aop/AfterReturningAdvice.html

The @Bean annotation is used to declare a method that returns an object that should be registered as a bean in the application context. The @ConditionalOnBean annotation is used to specify a condition for the bean creation based on the presence or absence of other beans in the application context. The name attribute of this annotation can be used to specify the bean name or names that must be present or absent for the condition to match. However, this approach is less flexible than using the value or type attribute, which can specify the bean class or classes that must be present or absent for the condition to match. Therefore, it is recommended to use @ConditionalOnBean(DataSource.class) instead of @ConditionalOnBean(name= “dataSource”) for greater flexibility.

The JdbcTemplate class is a Spring class that simplifies the use of JDBC and helps to avoid common errors. It executes core JDBC workflow, leaving application code to provide SQL and extract results. To create a JdbcTemplate object, we need to pass a DataSource object as a constructor argument. The DataSource interface is a Java interface that represents a factory of connection objects. In this code, the jdbcTemplate() method takes a DataSource object as a parameter and returns a new JdbcTemplate object. This method is annotated with @Bean and @ConditionalOnBean(name= “dataSource”), which means that it will only create a JdbcTemplate bean when there is already a bean named dataSource in the application context.

The JdbcTemplate class provides various methods to execute queries and manipulate the query results. Depending on the query and the expected result type, we can choose from the following three types of objects that can be returned from a JdbcTemplate query:

A. Generic Maps

This is true because the JdbcTemplate.queryForList method returns a List of Map objects, where each Map represents a row of the query result. The Map keys are the column names and the Map values are the column values1. For example:

List> results = jdbcTemplate.queryForList(“SELECT * FROM EMPLOYEE”); for (Map row : results) { System.out.println(row.get(“NAME”) + " " + row.get(“SALARY”)); }

B. Simple types (int, long, String, etc)

This is true because the JdbcTemplate.queryForObject method can return a single value of a simple type, such as int, long, String, etc. This method is useful for running queries that return a single row and a single column2. For example:

int count = jdbcTemplate.queryForObject(“SELECT COUNT(*) FROM EMPLOYEE”, Integer.class); System.out.println("Number of employees: " + count);

D. User defined types

This is true because the JdbcTemplate.query method can return a List of user defined types, such as custom classes or beans. This method takes a RowMapper as an argument, which is an interface that maps each row of the query result to an instance of the user defined type3. For example:

public class Employee { private String name; private int salary; // getters and setters }

public class EmployeeRowMapper implements RowMapper { @Override public Employee mapRow(ResultSet rs, int rowNum) throws SQLException { Employee employee = new Employee(); employee.setName(rs.getString(“NAME”)); employee.setSalary(rs.getInt(“SALARY”)); return employee; } }

List employees = jdbcTemplate.query(“SELECT * FROM EMPLOYEE”, new EmployeeRowMapper()); for (Employee employee : employees) { System.out.println(employee.getName() + " " + employee.getSalary()); }