- JBoss Weld CDI for Java Platform
- Ken Finnegan
- 298字
- 2021-08-13 16:49:55
Resolving Weld deployment errors
Weld will abort the deployment of our application and provide helpful error messages in the server log, when it's unable to identify a single bean for each injection point with typesafe resolution. We would expect to see one or more of unsatisfied or ambiguous dependency errors in this situation.
An unsatisfied dependency occurs when there is not a single bean that is eligible for injection into an injection point. This can be resolved as follows:
- By creating a bean that implements the bean type of the injection point and declares all the qualifier annotations present at the injection point
- If we already have a bean of the correct bean type and all the qualifier annotations in our application, check whether the bean is on the classpath of the bean archive that contains the injection point with the error
- With
beans.xml, enable an@Alternativebean of the correct bean type and qualifier annotations
An ambiguous dependency occurs when there is more than a single bean eligible for injection into an injection point. This can be resolved with the help of the following steps:
- Add a new
@Qualifierto disambiguate between the bean implementations that are eligible for injection. - Mark all but one of the bean implementations with
@Alternative, thus disabling them by default. - Relocate the bean implementations into a separate bean archive that is not on the classpath of the injection point.
- With
beans.xml, disable all but one@Alternativebean that are eligible for injection to that injection point.
Note
There may be occasions where we do legitimately have an injection point with multiple beans that are eligible. In this instance, we need to use Instance as the bean type of the injection point. We will cover this in the last section of this chapter.