spring-boot-dependency-injection

Name: spring-boot-dependency-injection
Author: giuseppe-trisciuoglio

1.6kinstalls36forks

How to install spring-boot-dependency-injection?

giuseppe-trisciuoglio/developer-kit/spring-boot-dependency-injection

$npx -y skills add giuseppe-trisciuoglio/developer-kit --skill spring-boot-dependency-injection

Installs into the current project.

Summary

Provides dependency injection patterns for Spring Boot projects, including constructor-first design, optional collaborator handling, bean selection, and wiring validation. Use when creating services and configurations, replacing field injection, or troubleshooting ambiguous or fr

Files · 1

View on GitHub

SKILL.md

1	# Spring Boot Dependency Injection
2
3	## Overview
4
5	Provides constructor-first dependency injection patterns for Spring Boot:
6	- mandatory collaborators via constructor injection
7	- optional collaborators via `ObjectProvider` or no-op fallbacks
8	- bean selection via `@Primary` and `@Qualifier`
9	- validation via minimal context tests before full integration
10
11	## When to Use
12
13	Use this skill when:
14	- creating a new `@Service`, `@Component`, `@Repository`, or `@Configuration` class
15	- replacing field injection in legacy Spring code
16	- resolving multiple beans of the same type with qualifiers or primary beans
17	- handling optional features, adapters, or integrations without null-driven wiring
18	- reviewing circular dependencies or brittle context startup failures
19	- preparing code for direct constructor-based unit testing
20
21
22	## Instructions
23
24	### 1. Separate mandatory and optional collaborators
25
26	For each class, identify:
27	- mandatory collaborators required for correct behavior
28	- optional collaborators that enable integrations, caching, notifications, or feature-flagged behavior
29
30	Mandatory collaborators belong in the constructor. Optional ones need an explicit strategy such as `ObjectProvider`, conditional beans, or a no-op implementation.
31
32	### 2. Default to constructor injection
33
34	For application services and adapters:
35	- inject mandatory dependencies through the constructor
36	- keep injected fields `final`
37	- instantiate the class directly in unit tests without starting Spring
38
39	A single constructor is usually enough; `@Autowired` is unnecessary in that case.
40
41	### 3. Resolve optional behavior intentionally
42
43	Good options include:
44	- `ObjectProvider<T>` when lazy access is useful
45	- `@ConditionalOnProperty` or `@ConditionalOnMissingBean` when wiring should change by configuration
46	- a no-op implementation when the caller should not care whether the feature is enabled
47
48	Avoid nullable collaborators that leave runtime behavior ambiguous.
49
50	### 4. Use bean selection annotations only when needed
51
52	When multiple beans share the same type:
53	- use `@Primary` for the default implementation
54	- use `@Qualifier` for named variants
55	- keep the qualifier names stable and easy to grep
56
57	If selection rules become complex, move them into a dedicated configuration class instead of spreading them across services.
58
59	### 5. Keep wiring in configuration, not business code
60
61	Use `@Configuration` and `@Bean` methods when:
62	- the object comes from a third-party library
63	- conditional creation logic is needed
64	- you need environment-specific wiring or explicit composition
65
66	Business services should not know how infrastructure collaborators are instantiated.
67
68	### 6. Validate wiring explicitly
69
70	After writing a new service or configuration:
71
72	1. Verify the bean loads with a minimal context test:
73	```java
74	@SpringBootTest
75	@ContextConfiguration(classes = UserService.class)
76	class UserServiceWiringTest {
77	@Autowired UserService userService;
78	@Test void serviceIsInstantiated() { assertNotNull(userService); }
79	}
80	```
81	2. Run constructor-based unit tests for service behavior (no Spring needed).
82	3. Add slice tests only when MVC, JPA, or messaging integration must be verified.
83	4. Reserve `@SpringBootTest` for container-wide wiring validation.
84
85	Failures at step 1 indicate wiring issues before business logic is added.
86
87	## Examples
88
89	### Example 1: Constructor-first application service
90
91	```java
92	@Service
93	public class UserService {
94
95	private final UserRepository userRepository;
96	private final EmailSender emailSender;
97
98	public UserService(UserRepository userRepository, EmailSender emailSender) {
99	this.userRepository = userRepository;
100	this.emailSender = emailSender;
101	}
102
103	public User register(UserRegistrationRequest request) {
104	User user = userRepository.save(User.from(request));
105	emailSender.sendWelcome(user);
106	return user;
107	}
108	}
109	```
110
111	This class is easy to instantiate directly in a unit test with mocks.
112
113	### Example 2: Optional dependency with a no-op fallback
114
115	```java
116	@Service
117	public class ReportService {
118
119	private final ReportRepository reportRepository;
120	private final NotificationGateway notificationGateway;
121
122	public ReportService(
123	ReportRepository reportRepository,
124	ObjectProvider<NotificationGateway> notificationGatewayProvider
125	) {
126	this.reportRepository = reportRepository;
127	this.notificationGateway = notificationGatewayProvider.getIfAvailable(NotificationGateway::noOp);
128	}
129	}
130	```
131
132	This keeps optional behavior explicit without leaking `null` handling th

People who liked this also viewed

6 picks

Type

spring-boot-dependency-injection

1.6kinstalls36forks

View on GitHub

How to install spring-boot-dependency-injection?

giuseppe-trisciuoglio/developer-kit/spring-boot-dependency-injection

$npx -y skills add giuseppe-trisciuoglio/developer-kit --skill spring-boot-dependency-injection

Installs into the current project.

Summary

Files · 1

View on GitHub

SKILL.md

1	# Spring Boot Dependency Injection
2
3	## Overview
4
5	Provides constructor-first dependency injection patterns for Spring Boot:
6	- mandatory collaborators via constructor injection
7	- optional collaborators via `ObjectProvider` or no-op fallbacks
8	- bean selection via `@Primary` and `@Qualifier`
9	- validation via minimal context tests before full integration
10
11	## When to Use
12
13	Use this skill when:
14	- creating a new `@Service`, `@Component`, `@Repository`, or `@Configuration` class
15	- replacing field injection in legacy Spring code
16	- resolving multiple beans of the same type with qualifiers or primary beans
17	- handling optional features, adapters, or integrations without null-driven wiring
18	- reviewing circular dependencies or brittle context startup failures
19	- preparing code for direct constructor-based unit testing
20
21
22	## Instructions
23
24	### 1. Separate mandatory and optional collaborators
25
26	For each class, identify:
27	- mandatory collaborators required for correct behavior
28	- optional collaborators that enable integrations, caching, notifications, or feature-flagged behavior
29
30	Mandatory collaborators belong in the constructor. Optional ones need an explicit strategy such as `ObjectProvider`, conditional beans, or a no-op implementation.
31
32	### 2. Default to constructor injection
33
34	For application services and adapters:
35	- inject mandatory dependencies through the constructor
36	- keep injected fields `final`
37	- instantiate the class directly in unit tests without starting Spring
38
39	A single constructor is usually enough; `@Autowired` is unnecessary in that case.
40
41	### 3. Resolve optional behavior intentionally
42
43	Good options include:
44	- `ObjectProvider<T>` when lazy access is useful
45	- `@ConditionalOnProperty` or `@ConditionalOnMissingBean` when wiring should change by configuration
46	- a no-op implementation when the caller should not care whether the feature is enabled
47
48	Avoid nullable collaborators that leave runtime behavior ambiguous.
49
50	### 4. Use bean selection annotations only when needed
51
52	When multiple beans share the same type:
53	- use `@Primary` for the default implementation
54	- use `@Qualifier` for named variants
55	- keep the qualifier names stable and easy to grep
56
57	If selection rules become complex, move them into a dedicated configuration class instead of spreading them across services.
58
59	### 5. Keep wiring in configuration, not business code
60
61	Use `@Configuration` and `@Bean` methods when:
62	- the object comes from a third-party library
63	- conditional creation logic is needed
64	- you need environment-specific wiring or explicit composition
65
66	Business services should not know how infrastructure collaborators are instantiated.
67
68	### 6. Validate wiring explicitly
69
70	After writing a new service or configuration:
71
72	1. Verify the bean loads with a minimal context test:
73	```java
74	@SpringBootTest
75	@ContextConfiguration(classes = UserService.class)
76	class UserServiceWiringTest {
77	@Autowired UserService userService;
78	@Test void serviceIsInstantiated() { assertNotNull(userService); }
79	}
80	```
81	2. Run constructor-based unit tests for service behavior (no Spring needed).
82	3. Add slice tests only when MVC, JPA, or messaging integration must be verified.
83	4. Reserve `@SpringBootTest` for container-wide wiring validation.
84
85	Failures at step 1 indicate wiring issues before business logic is added.
86
87	## Examples
88
89	### Example 1: Constructor-first application service
90
91	```java
92	@Service
93	public class UserService {
94
95	private final UserRepository userRepository;
96	private final EmailSender emailSender;
97
98	public UserService(UserRepository userRepository, EmailSender emailSender) {
99	this.userRepository = userRepository;
100	this.emailSender = emailSender;
101	}
102
103	public User register(UserRegistrationRequest request) {
104	User user = userRepository.save(User.from(request));
105	emailSender.sendWelcome(user);
106	return user;
107	}
108	}
109	```
110
111	This class is easy to instantiate directly in a unit test with mocks.
112
113	### Example 2: Optional dependency with a no-op fallback
114
115	```java
116	@Service
117	public class ReportService {
118
119	private final ReportRepository reportRepository;
120	private final NotificationGateway notificationGateway;
121
122	public ReportService(
123	ReportRepository reportRepository,
124	ObjectProvider<NotificationGateway> notificationGatewayProvider
125	) {
126	this.reportRepository = reportRepository;
127	this.notificationGateway = notificationGatewayProvider.getIfAvailable(NotificationGateway::noOp);
128	}
129	}
130	```
131
132	This keeps optional behavior explicit without leaking `null` handling th

People who liked this also viewed

6 picks

Type