@Named vs ManagedBean 注释问题 JEE8

问题描述

我正在做来自 Oracle 的 JEE8 教程并且在某一部分有问题。 https://javaee.github.io/tutorial/webapp003.html - 在这里您可以找到原始代码。

确切的问题是 @Named 注释在提交后出错：

/index.xhtml @20,43 value="#{hello.name}": Target Unreachable,identifier 'hello' resolved to null

但如果我使用已弃用的 @ManagedBean(name = "hello")，它会起作用。

而且我找不到任何地方，为什么？我什至在这里阅读了一些问题/文章，但没有人回答我的问题。有人可以解释为什么它会这样工作吗？我做错了什么？

堆栈是 JEE8、Maven 3.6.3、GlassFish 5.0.1

这是我唯一的豆子。它可以工作，但如果我取消注释 @Named 并注释 @ManagedBean，它将停止工作，并且在提交后出现错误。

package hello1;


import javax.enterprise.context.RequestScoped;
import javax.faces.bean.ManagedBean;
import javax.inject.Named;

@ManagedBean(name = "hello")
/*@Named*/
@RequestScoped
public class Hello {

    private String name;

    public Hello() {}

    public String getName() {
        return name;
    }

    public void setName(String user_name) {
        this.name = user_name;
    }
}

这是我的 *.xhtml 文件 index.xhtml

<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html lang="en"
      xmlns="http://www.w3.org/1999/xhtml"
      xmlns:h="http://xmlns.jcp.org/jsf/html">
    <h:head>
        <title>Facelets Hello Greeting</title>
    </h:head>
    <h:body>
        <h:form>
            <h:graphicImage url="#{resource['images:duke.waving.gif']}" 
                            alt="Duke waving his hand"/>
            <h2>Hello,my name is Duke. What's yours?</h2>
            <h:inputText id="username"
                         title="My name is: "
                         value="#{hello.name}"
                         required="true"
                         requiredMessage="Error: A name is required."
                         maxlength="25" />
            <p></p>
            <h:commandButton id="submit" value="Submit" 
                             action="response" />
            <h:commandButton id="reset" value="Reset" type="reset" />
        </h:form>
        <div class="messagecolor">
            <h:messages showSummary="true" 
                        showDetail="false"
                        errorStyle="color: #d20005" 
                        infoStyle="color: blue"/>
        </div>
    </h:body>
</html>

响应.xhtml

<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
   "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html lang="en"
     xmlns="http://www.w3.org/1999/xhtml"
     xmlns:h="http://xmlns.jcp.org/jsf/html">
   <h:head>
       <title>Facelets Hello Response</title>
   </h:head>
   <h:body>
       <h:form>
           <h:graphicImage url="#{resource['images:duke.waving.gif']}" 
                           alt="Duke waving his hand"/>
           <h2>Hello,#{hello.name}!</h2>
           <p></p>
           <h:commandButton id="back" value="Back" action="index" />
       </h:form>
   </h:body>
</html>

web.xml 文件：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <context-param>
        <param-name>javax.faces.PROJECT_STAGE</param-name>
        <param-value>Development</param-value>
    </context-param>
    <servlet>
        <servlet-name>Faces Servlet</servlet-name>
        <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>Faces Servlet</servlet-name>
        <url-pattern>*.xhtml</url-pattern>
    </servlet-mapping>
    <session-config>
        <session-timeout>
            30
        </session-timeout>
    </session-config>
    <welcome-file-list>
        <welcome-file>index.xhtml</welcome-file>
    </welcome-file-list>
</web-app>

pom.xml 文件：

<?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>com.example</groupId>
    <artifactId>hello1-custom</artifactId>
    <version>1.0-SNAPSHOT</version>
    <name>hello1-custom</name>
    <packaging>war</packaging>

    <properties>
        <maven.compiler.target>1.8</maven.compiler.target>
        <maven.compiler.source>1.8</maven.compiler.source>
        <junit.version>5.7.0</junit.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>javax</groupId>
            <artifactId>javaee-api</artifactId>
            <version>8.0.1</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-api</artifactId>
            <version>${junit.version}</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-engine</artifactId>
            <version>${junit.version}</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>3.3.0</version>
            </plugin>
        </plugins>
    </build>
</project>

解决方法

暂无找到可以解决该程序问题的有效方法，小编努力寻找整理中！

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annotations annotations java java managed-bean maven maven xml xml xml xml xml xml xml