我有JSF：
<p:graphicImage value="#{chatView.userPhoto}">
<f:param name="userId" value="#{user.id}"/>
</p:graphicImage>
user.id有效我已查看。
和豆：
@ManagedBean
@ViewScoped
public class ChatView extends BaseView {
/*
* Injecting managed beans in each other
* http://balusc.blogspot.com/2011/09/communication-in-jsf-20.html#InjectingManagedBeansInEachOther
*/
@ManagedProperty("#{chatUsers}")
private ChatUsers users;
public StreamedContent getUserPhoto() {
// there output is {}
System.out.println(FacesContext.getCurrentInstance().getExternalContext().getRequestParameterMap());
return new DefaultStreamedContent();
}
}
但是我在requestParameterMap的调试输出中有空映射。知道为什么吗？
更新：
我使用这样的pom.xml创建了一个简单的项目：
<?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>grim</groupId>
<artifactId>grim</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<version.jboss.bom>9.0.0.CR1</version.jboss.bom>
<version.primefaces>5.2</version.primefaces>
<version.atmosphere>2.3.1</version.atmosphere>
<version.jboss.logging>3.2.1.Final</version.jboss.logging>
</properties>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.wildfly.bom</groupId>
<artifactId>jboss-javaee-7.0-wildfly-with-tools</artifactId>
<version>${version.jboss.bom}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<!-- First declare the APIs we depend on and need for compilation. All
of them are provided by JBoss WildFly -->
<!-- Import the CDI API, we use provided scope as the API is included in
JBoss WildFly -->
<dependency>
<groupId>javax.enterprise</groupId>
<artifactId>cdi-api</artifactId>
<scope>provided</scope>
</dependency>
<!-- Import the Common Annotations API (JSR-250), we use provided scope
as the API is included in JBoss WildFly -->
<dependency>
<groupId>org.jboss.spec.javax.annotation</groupId>
<artifactId>jboss-annotations-api_1.2_spec</artifactId>
<scope>provided</scope>
</dependency>
<!-- Import the JAX-RS API, we use provided scope as the API is included
in JBoss WildFly -->
<dependency>
<groupId>org.jboss.resteasy</groupId>
<artifactId>jaxrs-api</artifactId>
<scope>provided</scope>
</dependency>
<!--Hibernate-->
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<scope>provided</scope>
</dependency>
<!-- Import the JPA API, we use provided scope as the API is included in
JBoss WildFly -->
<dependency>
<groupId>org.hibernate.javax.persistence</groupId>
<artifactId>hibernate-jpa-2.1-api</artifactId>
<scope>provided</scope>
</dependency>
<!-- Import the EJB API, we use provided scope as the API is included in
JBoss WildFly -->
<dependency>
<groupId>org.jboss.spec.javax.ejb</groupId>
<artifactId>jboss-ejb-api_3.2_spec</artifactId>
<scope>provided</scope>
</dependency>
<!-- JSR-303 (Bean Validation) Implementation -->
<!-- Provides portable constraints such as @Email -->
<!-- Hibernate Validator is shipped in JBoss WildFly -->
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator</artifactId>
<scope>provided</scope>
<exclusions>
<exclusion>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
</exclusion>
</exclusions>
</dependency>
<!-- Import the JSF API, we use provided scope as the API is included in
JBoss WildFly -->
<dependency>
<groupId>org.jboss.spec.javax.faces</groupId>
<artifactId>jboss-jsf-api_2.2_spec</artifactId>
<scope>provided</scope>
</dependency>
<!-- Now we declare any tools needed -->
<!-- Annotation processor to generate the JPA 2.0 metamodel classes for
typesafe criteria queries -->
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-jpamodelgen</artifactId>
<scope>provided</scope>
</dependency>
<!-- Annotation processor that raising compilation errors whenever constraint
annotations are incorrectly used. -->
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator-annotation-processor</artifactId>
<scope>provided</scope>
</dependency>
<!-- Needed for running tests (you may also use TestNG) -->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
<!-- Optional, but highly recommended -->
<!-- Arquillian allows you to test enterprise code such as EJBs and Transactional(JTA)
JPA from JUnit/TestNG -->
<dependency>
<groupId>org.jboss.arquillian.junit</groupId>
<artifactId>arquillian-junit-container</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.jboss.arquillian.protocol</groupId>
<artifactId>arquillian-protocol-servlet</artifactId>
<scope>test</scope>
</dependency>
<!-- Import the Servlet API, we use provided scope as the API is included in JBoss WildFly. -->
<dependency>
<groupId>org.jboss.spec.javax.servlet</groupId>
<artifactId>jboss-servlet-api_3.1_spec</artifactId>
<scope>provided</scope>
</dependency>
<!--PrimeFaces-->
<dependency>
<groupId>org.primefaces</groupId>
<artifactId>primefaces</artifactId>
<version>${version.primefaces}</version>
</dependency>
<!--Atmosphere-->
<dependency>
<groupId>org.atmosphere</groupId>
<artifactId>atmosphere-runtime</artifactId>
<version>${version.atmosphere}</version>
<exclusions>
<exclusion>
<artifactId>slf4j-api</artifactId>
<groupId>org.slf4j</groupId>
</exclusion>
</exclusions>
</dependency>
<!--Jboss Logging-->
<dependency>
<groupId>org.jboss.logging</groupId>
<artifactId>jboss-logging</artifactId>
<version>${version.jboss.logging}</version>
<scope>provided</scope>
</dependency>
</dependencies>
</project>
查看：
@ManagedBean
@ViewScoped
public class TestView {
public StreamedContent getImg() {
FacesContext context = FacesContext.getCurrentInstance();
if (context.getCurrentPhaseId() == PhaseId.RENDER_RESPONSE) {
// So, we're rendering the HTML. Return a stub StreamedContent so that it will generate right URL.
return new DefaultStreamedContent();
}
else {
// So, browser is requesting the image. Return a real StreamedContent with the image bytes.
String studentId = context.getExternalContext().getRequestParameterMap().get("shashistId");
Shashist student = shashistService.find(Long.valueOf(studentId));
return new DefaultStreamedContent(new ByteArrayInputStream(student.getPhoto()));
}
}
}
和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 xmlns="http://www.w3.org/1999/xhtml"
xmlns:h="http://xmlns.jcp.org/jsf/html"
xmlns:ui="http://xmlns.jcp.org/jsf/facelets"
xmlns:p="http://primefaces.org/ui"
xmlns:f="http://xmlns.jcp.org/jsf/core">
<f:view>
<h:outputLabel value="Hello, world"/>
<p:graphicImage value="#{testView.img}">
<f:param value="1" name="s"/>
</p:graphicImage>
</f:view>
</html>
但无论如何我在调试输出中得到空的请求参数映射。
答案 0 :(得分：0)
感谢这个回答https://stackoverflow.com/a/25425111/836701我找到了解决方案。问题出现在@ViewScope中，它应该是@SessionScope，用于从f：param获取参数。