无法使用上下文获取属性：属性占位符（Spring）

Question

我正在尝试从“文件”中读取属性，但无法获得相同的结果。

web.xml

<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>classpath:ApplicationContext.xml</param-value>
</context-param>
<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

ApplicationContext.xml

<context:annotation-config />
<context:component-scan base-package="com.jodo.image.*"></context:component-scan>

<context:property-placeholder location="file:/usr/local/jodo/opt/cms-image/db.properties"/>
<context:property-placeholder location="file:/usr/local/jodo/opt/cms-image/service.properties"/>

<util:properties id="systemPropertiesHolder" location="file:/usr/local/jodo/opt/cms-image/service.properties">
</util:properties>

第一次尝试

类 ThreadFileImageUpload

public class ThreadFileImageUpload extends Thread {
    private String rawImagePath;

    @Value("#{systemPropertiesHolder.rawImagePath}")
    public void setRawImagePath(String property){
        rawImagePath = property;
    }...

结果：rawImagePath 为空

第二次尝试

类 ThreadFileImageUpload

@Configuration
@ImportResource("classpath:properties-config.xml")
public class ThreadFileImageUpload extends Thread {
    private @Value("${rawImagePath}") String rawImagePath;

properties-config.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:p="http://www.springframework.org/schema/p" 
    xmlns:util="http://www.springframework.org/schema/util"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
        http://www.springframework.org/schema/beans/spring-beans.xsd
                http://www.springframework.org/schema/context
                http://www.springframework.org/schema/context/spring-context-2.5.xsd
                http://www.springframework.org/schema/util 
                http://www.springframework.org/schema/util/spring-util-3.0.xsd">
  <context:property-placeholder location="file:/usr/local/jodo/opt/cms-image/service.properties"/>
</beans>

结果：rawImagePath 为空

第三次尝试

类 ThreadFileImageUpload

@Configuration
@PropertySource("file:/usr/local/jodo/opt/cms-image/service.properties")
public class ThreadFileImageUpload extends Thread {
    @Autowired 
    Environment environment;
    private String rawImagePath;
    public void run() {
        if(environment == null){
                logger.info("environment is NULL");
            }
            rawImagePath = this.environment.getProperty("rawImagePath");
        ...

给java.lang.NullPointerException（环境本身为null）

第四次尝试

类 ThreadFileImageUpload

public class ThreadFileImageUpload extends Thread { 
    @Value("${rawImagePath}")
    private String rawImagePath;

结果：rawImagePath 为空

第五次尝试

ApplicationContext.xml（现在将所有文件放在一个属性占位符中）

<context:property-placeholder location="file:/usr/local/jodo/opt/cms-image/db.properties, file:/usr/local/jodo/opt/cms-image/service.properties"/>

类 ThreadFileImageUpload

public class ThreadFileImageUpload extends Thread { 
    @Value("${rawImagePath}")
    private String rawImagePath;

结果：rawImagePath 为空

第六次尝试

类 ThreadFileImageUpload

package com.jodo.image.util;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
@Component
public class ThreadFileImageUpload extends Thread { 
    @Value("#{systemPropertiesHolder.rawImagePath}")
    private String rawImagePath;

AppliactionContext.xml

<context:annotation-config />
<context:component-scan base-package="com.jodo.image.*"></context:component-scan>
<util:properties id="systemPropertiesHolder" location="file:/usr/local/jodo/opt/cms-image/service.properties">
</util:properties>

仍然是 null

我确定属性文件有必填字段

[root@localhost /]# cat /usr/local/jodo/opt/cms-image/service.properties 
rawImagePath=/var/jodo-images/raw/

我仍然被困在同一个地方。

Answer 1

无论您使用@Value 注入属性，您要注入的类都必须是一个Spring bean。要做到这一点，您需要使用 @Component 注释 ThreadFileImageUpload 并确保组件扫描中的包中的类，或者您需要手动添加该 bean（在本例中为 ApplicationContext.xml）

Answer 2

要使@Value 工作，ThreadFileImageUpload 实例必须是 Spring 托管组件。请注意，使用“new”创建的实例不由 Spring 管理。参考手册here和here可以帮助你理解Spring bean和组件扫描。

Answer 3

我认为您缺少属性的名称（根）。 看到这个http://forum.spring.io/forum/spring-projects/container/61645-value-and-propertyplaceholderconfigurer

如果文件是service.properties 而你有

`<util:properties id="service" location="classpath:com/acme/app/service.properties"/>`

那就试试@Value("#{service.rawImagePath}")