SONARJAVA-5284 Create rule S7178: Injecting data into static fields i…

…s not supported by Spring (#4611)

rules/S7178/java/metadata.json

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+{
+  "title": "Injecting data into static fields is not supported by Spring",
+  "type": "CODE_SMELL",
+  "status": "ready",
+  "remediation": {
+    "func": "Constant\/Issue",
+    "constantCost": "5min"
+  },
+  "tags": [
+    "spring"
+  ],
+  "defaultSeverity": "Major",
+  "ruleSpecification": "RSPEC-7178",
+  "sqKey": "S7178",
+  "scope": "Main",
+  "defaultQualityProfiles": ["Sonar way"],
+  "quickfix": "unknown",
+  "code": {
+    "impacts": {
+      "MAINTAINABILITY": "LOW",
+      "RELIABILITY": "HIGH",
+      "SECURITY": "LOW"
+    },
+    "attribute": "LOGICAL"
+  }
+}

rules/S7178/java/rule.adoc

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+== Why is this an issue?
+
+Spring dependency injection framework does not support injecting data into static fields. When @Value, @Inject, or @Autowired are applied to static fields, they are ignored.
+
+=== What is the potential impact?
+
+* *Null Values*: Uninitialized static fields annotated with @Value, @Inject, or @Autowired will not be initialized by Spring, potentially causing NullPointerException at runtime.
+* *Confusing Code*: The presence of injection annotations on static fields can mislead developers into believing that the fields will be populated by Spring.
+
+This rule raises an issue when a static field is annotated with @Value, @Inject, or @Autowired.
+
+== How to fix it
+
+Either use an instance field instead of a static field or remove the @Value, @Inject, or @Autowired annotation and initialize the field.
+
+=== Code examples
+
+==== Noncompliant code example
+
+[source,java,diff-id=1,diff-type=noncompliant]
+----
+@Component
+public class MyComponent {
+
+    @Value("${my.app.prop}")
+    private static SomeDependency dependency; // non compliant, @Value will be ignored and no value will be injected
+    // ...
+}
+----
+
+==== Compliant solution
+
+[source,java,diff-id=1,diff-type=compliant]
+----
+@Component
+public class MyComponent {
+
+    @Value("${my.app.prop}")
+    private final SomeDependency dependency;
+    // ...
+}
+----
+
+== Resources
+=== Articles & blog posts
+* Java Guides - https://www.baeldung.com/spring-inject-static-field[Injecting a Value in a Static Field in Spring]

rules/S7178/metadata.json

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+{
+}