20 MyBatis Interview Questions and Answers
Prepare for the types of questions you are likely to be asked when interviewing for a position where MyBatis will be used.
MyBatis is a persistence framework that maps Java objects to SQL databases. It is an alternative to JDBC and Hibernate. If you are applying for a Java development position, it is likely that the interviewer will ask you questions about MyBatis. Answering these questions correctly can help you demonstrate your knowledge and expertise in Java development. In this article, we will review some common MyBatis interview questions and provide example answers.
MyBatis Interview Questions and Answers
Here are 20 commonly asked MyBatis interview questions and answers to prepare you for your interview:
1. What is MyBatis?
MyBatis is a Java persistence framework that makes it easier to work with SQL databases. MyBatis can map Java objects to database tables and vice versa. MyBatis also provides a SQL mapping engine that lets you write SQL queries in a more natural Java style.
2. Can you explain the architecture of MyBatis?
MyBatis is a data mapping framework that helps map Java objects to SQL databases. It is designed to be simple and lightweight, yet still powerful enough to handle complex data mapping scenarios. MyBatis uses a SQL Mapper to map Java objects to SQL databases, and a Plugin to handle custom extensions.
3. What are some advantages of using MyBatis over JDBC?
MyBatis is a persistence framework which offers a number of advantages over using JDBC directly. MyBatis eliminates the need for manual mapping of objects to database tables, and it also provides built-in caching to improve performance. MyBatis can also generate SQL dynamically, which can be helpful in situations where the structure of the database may change frequently.
4. How can you configure a data source for MyBatis?
You can configure a data source for MyBatis by specifying the driver class, URL, username, and password in the configuration file. You can also specify a connection pool size and other parameters.
5. What do you understand by SQL mappers in MyBatis?
SQL mappers are files that contain SQL statements and mapping metadata. MyBatis uses these mappers to access databases. Each mapper is responsible for a single table.
6. What’s the difference between @Select and @Results annotations?
The @Select annotation is used to specify a custom SQL query to be run when a method is invoked. The @Results annotation is used to map the results of the SQL query to Java objects.
7. What are the different types of result maps available in MyBatis?
There are four different types of result maps available in MyBatis:
1. Nested Result Maps: These result maps allow you to map the results of one SQL statement into the properties of another JavaBean.
2. Associative Result Maps: These result maps allow you to map the results of one SQL statement into the properties of another JavaBean, but with the addition of an extra column that will act as a key.
3. Auto-Mapping Result Maps: These result maps allow MyBatis to automatically map columns from the SQL result set to JavaBean properties, without the need for an explicit mapping.
4. Complex Result Maps: These result maps allow you to map the results of one SQL statement into multiple JavaBeans.
8. Can you explain how to use a custom type handler with MyBatis? How does it work?
A custom type handler is a way to tell MyBatis how to map a particular Java type to a corresponding database type. For example, you might want to use a custom type handler to map a Java enum to a VARCHAR column in your database. To do this, you would first create a custom type handler that implements the org.apache.ibatis.type.TypeHandler interface. This interface defines methods for setting and getting values from a prepared statement or resultset. Once you have created your custom type handler, you need to register it with MyBatis. This can be done in the configuration file. Finally, you need to specify that you want to use the custom type handler for a particular Java type when mapping SQL statements.
9. Can you give an example of how to use dynamic SQL statements in MyBatis?
MyBatis offers a number of features for working with dynamic SQL statements. For example, you can use the
10. Is it possible to integrate Spring Boot with MyBatis? If yes, then how?
Yes, it is possible to integrate Spring Boot with MyBatis. You can do so by adding the following dependency to your pom.xml file:
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11. What happens if the value of a parameter doesn’t match the target type specified in the parameterType attribute in MyBatis?
If the value of a parameter doesn’t match the target type specified in the parameterType attribute in MyBatis, then an exception will be thrown.
12. When should you use multiple parameters instead of one single parameter in a statement?
In general, you should use multiple parameters when you need to pass in more than one value to a statement. For example, if you need to insert multiple values into a table, you would use multiple parameters. This allows for better organization and prevents confusion.
13. What are tags used for in MyBatis?
Tags are used in MyBatis to mark where SQL statements should be placed in the XML mapping file. This allows for greater flexibility in how the SQL statements are organized and makes it easier to maintain the mapping file.
14. What is the default fetch size used by MyBatis when executing queries?
The default fetch size used by MyBatis is 10.
15. What is the best way to handle large queries in MyBatis? Why?
The best way to handle large queries in MyBatis is to use the paging functionality built into the framework. This way, you can break up your large query into smaller pieces, and process each piece separately. This can help improve performance and avoid OutOfMemoryErrors.
16. What is the usage of environment properties in MyBatis?
Environment properties are used to configure MyBatis to connect to different databases or data sources. This is useful if you need to connect to multiple databases within the same application.
17. What is the purpose of the CacheRef tag in MyBatis?
The CacheRef tag is used to reference another cache by name. This is useful if you have multiple caches in your MyBatis configuration and you want to reference one cache from another.
18. Can you explain what lazy loading is? In which situations would you want to enable or disable this feature?
Lazy loading is a feature that allows MyBatis to delay loading of related objects until they are needed. This can be useful in situations where related objects are not always needed, as it can improve performance by avoiding unnecessary database queries. Lazy loading can be enabled or disabled on a per-mapping basis.
19. What is the significance of the @MapKey annotation in MyBatis?
The @MapKey annotation is used to specify the column that should be used as the key for a map that is being returned by a MyBatis query. This is important because it allows you to control how the data in the map is accessed. Without the @MapKey annotation, the data in the map would be accessed by its column name, which can be difficult to remember.
20. Why is MyBatis considered better than Hibernate?
MyBatis is often considered better than Hibernate because it is much simpler and easier to use. It is also more flexible, because it does not require you to use annotations or XML files to configure mapping. MyBatis is also more efficient, because it uses a dynamic SQL approach that only generates the SQL that is actually needed, rather than Hibernate’s approach of generating SQL for all possible queries.