running uber jar spring @value null

Question

我需要从我的maven模块(Java+Spring)及其依赖项创建一个单独的可执行jar。所以我在我的POM中包含了maven-shade-plugin，看起来它打包了所有需要的东西。

当我运行这个jar时，它以NullPointerException失败。看起来它没有找到@Value在我的主类中引用的值，我最终得到了一个NPE。我确实看到applicationContext和properties文件在jar中。这可能是什么原因呢?

applicationContext.xml -

<context:property-placeholder location="classpath:props.properties" ignore-unresolvable="true"/>

Main.java -

@Value("${property.inside.props.file}")
private String propertyName;

pom.xml -

<plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-shade-plugin</artifactId>
            <version>2.4.1</version>
            <executions>
              <execution>
                <phase>package</phase>
                <goals>
                  <goal>shade</goal>
                </goals>
                <configuration>
                <transformers>
                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                    <manifestEntries>
                        <Main-Class>com.sloan.Main.java</Main-Class>
                    </manifestEntries>
                </transformer>
        <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
                  <resource>META-INF/spring.handlers</resource>
                </transformer>
                <transformer implementation="org.apache.maven.plugins.shade.resource.AppendingTransformer">
                  <resource>META-INF/spring.schemas</resource>
                </transformer>
            </transformers>
                 <filters>
                 <filter>
                      <artifact>*:*</artifact>
                      <excludes>
                        <exclude>META-INF/*.SF</exclude>
                        <exclude>META-INF/*.DSA</exclude>
                        <exclude>META-INF/*.RSA</exclude>
                      </excludes>
                    </filter>
                    </filters>
                </configuration>
              </execution>
            </executions>
          </plugin>

我试过用汇编插件做同样的事情，但这也带来了NPE。

Answer 1

我发现我错过了什么，加载Spring上下文!现在main。java首先加载上下文-

ApplicationContext applicationContext = new ClassPathXmlApplicationContext("META-INF\spring\applicationContext.xml");

重新安装后一切正常

Answer 2

您缺少负责解析此注释的@Bean

将此bean添加到您的配置类

@Bean
public static PropertyPlaceholderConfigurer getValueResolver()
{
    return new PropertyPlaceholderConfigurer();
}

的基于XML的教程看这里http://www.mkyong.com/spring/spring-propertyplaceholderconfigurer-example/