16f6c0aecf
Inline adoc files when they are included exactly once. Also fix language tags because this inlining gives us better information on what language the code is written in.
67 lines
1.8 KiB
Plaintext
67 lines
1.8 KiB
Plaintext
== Why is this an issue?
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Field injection seems like a tidy way to get your classes what they need to do their jobs, but it's really a ``++NullPointerException++`` waiting to happen unless all your class constructors are ``++private++``. That's because any class instances that are constructed by callers, rather than instantiated by a Dependency Injection framework compliant with the JSR-330 (Spring, Guice, ...), won't have the ability to perform the field injection.
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Instead ``++@Inject++`` should be moved to the constructor and the fields required as constructor parameters.
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This rule raises an issue when classes with non-``++private++`` constructors (including the default constructor) use field injection.
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=== Noncompliant code example
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[source,java]
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----
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class MyComponent { // Anyone can call the default constructor
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@Inject MyCollaborator collaborator; // Noncompliant
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public void myBusinessMethod() {
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collaborator.doSomething(); // this will fail in classes new-ed by a caller
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}
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}
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----
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=== Compliant solution
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[source,java]
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----
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class MyComponent {
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private final MyCollaborator collaborator;
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@Inject
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public MyComponent(MyCollaborator collaborator) {
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Assert.notNull(collaborator, "MyCollaborator must not be null!");
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this.collaborator = collaborator;
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}
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public void myBusinessMethod() {
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collaborator.doSomething();
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}
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}
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----
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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=== Message
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Use constructor injection for this field.
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'''
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== Comments And Links
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(visible only on this page)
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=== on 14 Oct 2016, 13:31:17 Freddy Mallet wrote:
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As decided with the Java team, let's remove this rule from the default "Sonar way" quality profile. See SONARJAVA-1880.
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endif::env-github,rspecator-view[]
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