WELD-001408：在注入点 [BackedAnnotatedField] @Inject 带有限定符 @Default 的 UserService 类型的依赖项不满足

Question

I get an error while @Inject . I don't understand why.

My Application Server: GlassFish 4.1.2

The server gives an error when I @Inject my Class I created

java.io.IOException: com.sun.enterprise.admin.remote.RemoteFailureException: Error occurred during deployment: Exception while loading the app : CDI deployment failure:WELD-001408: Unsatisfied dependencies for type UserService with qualifiers @Default at injection point [BackedAnnotatedField] @Inject private jobs.SignUpCDIB.userServiceat jobs.SignUpCDIB.userService(SignUpCDIB.java:0)

The server gives an error when I @Inject my Class I created

package jobs;

import services.UserService;
import javax.enterprise.context.ConversationScoped;
import javax.inject.Inject;
import javax.inject.Named;
import java.io.Serializable;

@Named
@ConversationScoped
public class SignUpCDIB implements Serializable {

    private static final long serialVersionUID = 1L;

    @Inject
    private UserService userService;
}

I'm trying to inject it to another class like:

package services;

import jobs.User;

public interface UserService {

    void save(User user);
}

UserService implement java class

package services;

import jobs.User;

import java.io.Serializable;

public class UserServiceImpl implements UserService, Serializable {
    @Override
    public void save(User user) {

    }
}

Maven pom xml file

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>groupId</groupId>
    <artifactId>loginTutorials1</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>com.sun.faces</groupId>
            <artifactId>jsf-api</artifactId>
            <version>2.2.13</version>
        </dependency>
        <dependency>
            <groupId>com.sun.faces</groupId>
            <artifactId>jsf-impl</artifactId>
            <version>2.2.13</version>
        </dependency>

        <dependency>
            <groupId>javax.inject</groupId>
            <artifactId>javax.inject</artifactId>
            <version>1</version>
        </dependency>

        <dependency>
            <groupId>javax.enterprise</groupId>
            <artifactId>cdi-api</artifactId>
            <version>1.2</version>
        </dependency>

        <dependency>
            <groupId>javax</groupId>
            <artifactId>javaee-api</artifactId>
            <version>7.0</version>
        </dependency>
    </dependencies>
    <build>
        <pluginManagement>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <configuration>
                        <source>1.8</source>
                        <target>1.8</target>
                    </configuration>
                </plugin>
            </plugins>
        </pluginManagement>
    </build>
</project>```

Answer 1

The reason why you're getting this error is evident from the error message produced by the DI container. As you can see by this:

Unsatisfied dependencies for type UserService with qualifiers @Default at injection point

The container notifies you that there is no bean eligible for injection for the requested implementation (ie UserService is this case).

Adding the @Singleton annotation makes this visible to the DI container and at the same time automatically eligible for injection.

The annotation in question work pretty much in the same way as the @ConversationScoped you have on your other class, albeit with a few differences in the scope of which the bean is available.

I suggest you do a good read up on how bean and DI is handled in general.