Which of the following Java classes correctly models this nested property using @ConfigurationProperties?
A@ConfigurationProperties(prefix = "mail")
public class MailProperties {
private Server server;
public static class Server {
private String host;
private int port;
// getters and setters
}
// getters and setters for server
}
B@ConfigurationProperties(prefix = "mail.server")
public class MailProperties {
private String host;
private int port;
// getters and setters
}
C@ConfigurationProperties(prefix = "mail")
public class MailProperties {
private String host;
private int port;
// getters and setters
}
D@ConfigurationProperties(prefix = "mail.server")
public class MailProperties {
private Server server;
public static class Server {
private String host;
private int port;
// getters and setters
}
// getters and setters for server
}
Step-by-Step Solution
Solution:
Step 1: Understand nested property binding
Properties like mail.server.host require a class with prefix mail and a nested class Server to hold host and port.
Step 2: Analyze options
@ConfigurationProperties(prefix = "mail")
public class MailProperties {
private Server server;
public static class Server {
private String host;
private int port;
// getters and setters
}
// getters and setters for server
} correctly uses @ConfigurationProperties(prefix = "mail") with a nested Server class. @ConfigurationProperties(prefix = "mail.server")
public class MailProperties {
private String host;
private int port;
// getters and setters
} flattens properties incorrectly. @ConfigurationProperties(prefix = "mail")
public class MailProperties {
private String host;
private int port;
// getters and setters
} misses nesting. @ConfigurationProperties(prefix = "mail.server")
public class MailProperties {
private Server server;
public static class Server {
private String host;
private int port;
// getters and setters
}
// getters and setters for server
} uses prefix mail.server but still nests, which is inconsistent.
Final Answer:
@ConfigurationProperties(prefix="mail") with nested Server class -> Option A
Quick Check:
Nested class with prefix mail = A [OK]
Quick Trick:Use nested classes for nested property groups [OK]
Common Mistakes:
Using wrong prefix for nested properties
Flattening nested properties into one class
Missing getters/setters in nested class
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