0

环境：

  • 野蝇 22
  • 爪哇 11
  • JSF 2.3

我试图在 bean 中注入一个 ManagedProperty 并且我得到一个 NullPointerExcepion 但我不知道为什么会这样。缺少什么？

错误日志

21:35:25,994 SEVERE [javax.enterprise.resource.webcontainer.jsf.application] (default task-8) Error Rendering View[/index.xhtml]: java.lang.NullPointerException
    at com.sun.jsf-impl@2.3.14.SP02//com.sun.faces.cdi.ManagedPropertyProducer.evaluateExpressionGet(ManagedPropertyProducer.java:87)
    at com.sun.jsf-impl@2.3.14.SP02//com.sun.faces.cdi.ManagedPropertyProducer.lambda$new$0(ManagedPropertyProducer.java:60)
    at com.sun.jsf-impl@2.3.14.SP02//com.sun.faces.cdi.CdiProducer.create(CdiProducer.java:105)
    at com.sun.jsf-impl@2.3.14.SP02//com.sun.faces.cdi.ManagedPropertyProducer.create(ManagedPropertyProducer.java:38)
    at org.jboss.weld.core@3.1.5.Final//org.jboss.weld.contexts.unbound.DependentContextImpl.get(DependentContextImpl.java:64)
    ...

21:35:26,001 ERROR [io.undertow.request] (default task-8) UT005023: Exception handling request to /roscam/index.xhtml: javax.servlet.ServletException
    at javax.faces.api@3.0.0.SP04//javax.faces.webapp.FacesServlet.executeLifecyle(FacesServlet.java:725)
    at javax.faces.api@3.0.0.SP04//javax.faces.webapp.FacesServlet.service(FacesServlet.java:451)
    at io.undertow.servlet@2.2.4.Final//io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:74)
    ...
Caused by: java.lang.NullPointerException
    at com.sun.jsf-impl@2.3.14.SP02//com.sun.faces.cdi.ManagedPropertyProducer.evaluateExpressionGet(ManagedPropertyProducer.java:87)
    at com.sun.jsf-impl@2.3.14.SP02//com.sun.faces.cdi.ManagedPropertyProducer.lambda$new$0(ManagedPropertyProducer.java:60)
    at com.sun.jsf-impl@2.3.14.SP02//com.sun.faces.cdi.CdiProducer.create(CdiProducer.java:105)
    at com.sun.jsf-impl@2.3.14.SP02//com.sun.faces.cdi.ManagedPropertyProducer.create(ManagedPropertyProducer.java:38)
    ...
    ... 57 more

会话Bean

@Named
@SessionScoped
public class SessionBean implements Serializable {
    ...
    @Inject
    @ManagedProperty(value = "#{localeBean}")
    private LocaleBean localeB;//Error injecting bean NullPointerException
    ...
    @PostConstruct
    public void init() {
    ...

LocaleBean

@Named
@SessionScoped
public class LocaleBean implements Serializable {

   @PostConstruct
   public void init() {
...

索引.xhtml

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:h="http://java.sun.com/jsf/html"
      xmlns:f="http://java.sun.com/jsf/core"
      xmlns:p="http://primefaces.org/ui">

<h:head>
</h:head>

<h:body>
    <f:view locale="#{localeBean.locale}">
       hi there
        #{sessionBean.doNothing}
    </f:view>
</h:body>

</html>

pom.xml

...
<dependencies>
    <dependency>
        <groupId>jakarta.platform</groupId>
        <artifactId>jakarta.jakartaee-api</artifactId>
        <version>8.0.0</version>
        <scope>provided</scope>
    </dependency>
    <dependency>
        <groupId>org.primefaces</groupId>
        <artifactId>primefaces</artifactId>
        <version>10.0.0</version>
    </dependency>
    ...
4

3 回答 3

1

没有@ManagedProperty 就不能简单地注入一个LocaleBean 吗？

于 2021-05-14T23:19:12.500 回答
0

运行没有任何问题

  • 日食 4.18
  • 采用JDK 11.0.5
  • WildFly 22.0.0.Final（非预览版）
  • 莫哈拉 2.3.14.SP02

这里

但删除@ManagedProperty(value = "#{localeBean}")注释。

所以

package foo.bar;

import java.io.Serializable;
import javax.enterprise.context.SessionScoped;
import javax.inject.Named;

@SessionScoped
@Named
public class LocaleBean implements Serializable {
    private static final long serialVersionUID = 7584442178216104053L;
    private String locale;

    public String getLocale() {
        return locale;
    }
}

package foo.bar;

import java.io.Serializable;
import javax.enterprise.context.SessionScoped;
import javax.inject.Inject;
import javax.inject.Named;

@Named
@SessionScoped
public class SessionBean implements Serializable {
    private static final long serialVersionUID = -6657315612830810889L;
    @Inject
    private LocaleBean localeB;
    private String doNothing = "foobar";

    public String getDoNothing() {
        return doNothing;
    }
}

完美运行。

对于这个测试，你根本不需要 Maven 的东西。

如果出现其他错误，请尝试不使用 Primefaces。

而且应该是

<html xmlns="http://www.w3.org/1999/xhtml"
    xmlns:h="http://xmlns.jcp.org/jsf/html"
    xmlns:f="http://xmlns.jcp.org/jsf/core">

如果你得到一个

org.jboss.weld.exceptions.WeldException: WELD-001524: Unable to load proxy class for bean Managed Bean [class LocaleBean] with qualifiers [@Default @Any @Named] with class class LocaleBean
...
java.lang.ClassFormatError: Illegal class name "/LocaleBean$Proxy$_$$_WeldClientProxy" in class file /LocaleBean$Proxy$_$$_WeldClientProxy

错误，那么您必须将 bean 类放入包中：Weld 在默认包中为 EJB 类创建无效代理。在 Weld 3.1.7.Final 中修复。WildFly 22.0.0.Final 包含 Weld 3.1.5.Final，WildFly 23.0.0.Final 包含 Weld 3.1.6.Final...

另请参阅@ManagedProperty 的 CDI 替换。

于 2021-05-15T07:05:30.163 回答
-1

截至 jakartaee 8 ManagedProperty 已被弃用，正如我们在其api中看到的那样。

因此，不需要将@ManagedProperty 与@Injecton 一起使用。

于 2021-05-15T11:24:12.307 回答