使用Maven-assembly-plugin创建uber jar时，Jersey失败 [英] Jersey fails when creating uber jar with maven-assembly-plugin

问题描述

我创建了一个Maven球衣入门Web应用程序.另外，我还使用jetty插件在我的应用程序中嵌入了jetty服务器.

I have created a maven jersey starter webapp. Also I have embedded jetty server in my app using jetty plugin.

当我使用mvn jetty:run命令运行项目时，我的项目运行正常.

My project is working fine when I run my project using mvn jetty:run command.

但是当我使用mvn clean package命令打包我的项目并运行名称为jar-with-dependencies的jar文件时，该项目会在从jersey资源返回json响应时引发此异常.

But when I package my project using mvn clean package command and run the jar file which has name jar-with-dependencies the project throws this exception while returning a json response from a jersey resource.

严重程度:找不到针对媒体type = application/json，type = class com.nitish.freecharge.model.Count，genericType = class com.nitish.freecharge.model.Count的MessageBodyWriter.

这是我的pom.xml文件

Here is my pom.xml file

http://maven.apache.org/maven-v4_0_0.xsd>

http://maven.apache.org/maven-v4_0_0.xsd">

<modelVersion>4.0.0</modelVersion>

<groupId>com.nitish.freecharge</groupId>
<artifactId>wordcount</artifactId>
<packaging>war</packaging>
<version>2.0</version>
<name>wordcount</name>

<build>
    <finalName>wordcount</finalName>
    <resources>
        <resource>
            <directory>src/main/java</directory>
        </resource>
        <resource>
            <directory>src/main/resources</directory>
        </resource>
        <resource>
            <directory>src/main/webapp</directory>
        </resource>
    </resources>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>2.5.1</version>
            <inherited>true</inherited>
            <configuration>
                <source>1.7</source>
                <target>1.7</target>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.eclipse.jetty</groupId>
            <artifactId>jetty-maven-plugin</artifactId>
            <version>9.3.0.v20150612</version>
            <configuration>
                <scanIntervalSeconds>5</scanIntervalSeconds>
                <webApp>
                    <contextPath>/wordcount</contextPath>
                </webApp>
                <httpConnector>
                    <!--host>localhost</host -->
                    <port>9999</port>
                </httpConnector>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jar-plugin</artifactId>
            <version>2.4</version>
            <executions>
                <execution>
                    <id>package-jar</id>
                    <phase>package</phase>
                    <goals>
                        <goal>jar</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-assembly-plugin</artifactId>
            <version>2.6</version>
            <configuration>
                <finalName>awesomeProject</finalName>
                <descriptorRefs>
                    <descriptorRef>jar-with-dependencies</descriptorRef>
                </descriptorRefs>
                <appendAssemblyId>false</appendAssemblyId>
                <archive>
                    <manifest>
                        <mainClass>App</mainClass>
                    </manifest>
                </archive>
            </configuration>
            <executions>
                <execution>
                    <phase>package</phase>
                    <goals>
                        <goal>single</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>
<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.glassfish.jersey</groupId>
            <artifactId>jersey-bom</artifactId>
            <version>${jersey.version}</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

<dependencies>
    <dependency>
        <groupId>org.glassfish.jersey.core</groupId>
        <artifactId>jersey-server</artifactId>
    </dependency>
    <dependency>
        <groupId>org.glassfish.jersey.containers</groupId>
        <artifactId>jersey-container-servlet-core</artifactId>
    </dependency>
    <dependency>
        <groupId>org.glassfish.jersey.media</groupId>
        <artifactId>jersey-media-moxy</artifactId>
    </dependency>
    <dependency>
        <groupId>org.eclipse.jetty</groupId>
        <artifactId>jetty-server</artifactId>
        <version>9.3.8.v20160314</version>
    </dependency>
    <dependency>
        <groupId>org.eclipse.jetty</groupId>
        <artifactId>jetty-servlet</artifactId>
        <version>9.3.8.v20160314</version>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.4</version>
    </dependency>
</dependencies>
<properties>
    <jersey.version>2.22.2</jersey.version>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>

我在默认包中将主驱动程序类创建为App.java.这是我的App.java内容

I have created my Main Driver class as App.java in default package. Here is my App.java content

import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.servlet.ServletContextHandler;
import org.eclipse.jetty.servlet.ServletHolder;

public class App {
    public static void main(String []gg){

        Server server = new Server(9999);

        ServletContextHandler context = new ServletContextHandler(ServletContextHandler.NO_SESSIONS);
        context.setContextPath("/");
        server.setHandler(context);

        ServletHolder jerseyServlet = context.addServlet(org.glassfish.jersey.servlet.ServletContainer.class, "/wordcount/*");
        jerseyServlet.setInitOrder(1);
        jerseyServlet.setInitParameter("jersey.config.server.provider.packages","com.nitish.freecharge.resources");
        try {
            System.out.println("Starting the server..");
            server.start();
            System.out.println("Server started");
            server.join();
        } catch(Exception e) {
            System.out.println("Exception in starting the server ");
            e.printStackTrace();
        }
    }
}

这是我唯一的球衣资源类，它在启动服务器后访问我的项目URL时执行:

Here is my only jersey resource class which gets executed when I access my project url after starting the server :

package com.nitish.freecharge.resources;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.QueryParam;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.Response.Status;
import com.nitish.freecharge.dao.FileDAO;
import com.nitish.freecharge.model.Count;

/**
 * Root resource (exposed at "count" path) which handles HTTP GET method and returns the count value;
 */
@Path("/count")
public class CountResource {

    private FileDAO fileDAO=new FileDAO();

    /**
     * Method handling HTTP GET requests. The returned object will be sent
     * to the client as "application/json" media type.
     *
     * @return String that will be returned as a application/json response.
     */
    @GET
    @Produces(MediaType.APPLICATION_JSON)
    @QueryParam("query")
    public Response getWordCount(@QueryParam("query")String query) {
        Error error=null;
        Count count=null;
        try{   
            if(query!=null){
                query=query.trim();
                if(query.length()>0 && query.matches("^[A-Za-z]+$")){
                    long c=fileDAO.getCount(query.toLowerCase());
                    count=new Count(c);
                }else{
                    error=new Error("Some Error Occured.Please Try Again With a new word!");
                }
            }else{
                error=new Error("Some Error Occured.Please Try Again!");
            }
        }catch(Exception e){
            error=new Error(e.getMessage());
            return Response.status(Status.INTERNAL_SERVER_ERROR).entity(error).build();
        }
        if(count!=null){
            return Response.status(Status.OK).entity(count).build();
        }else{
            return Response.status(Status.BAD_REQUEST).entity(error).build();
        }
    }
}

打包并使用命令运行完整的嵌入式项目后 java -jar awesomeProject.jar

After packaging and run the complete embedded project using command java -jar awesomeProject.jar

我在服务器提示符下得到此输出

I get this output on the server prompt

我已经尝试了很多，但无法以解决该问题的方式打包我的嵌入式Web应用程序.我是Maven和包装的新手.请在我犯错的地方提供帮助.

I have tried a lot and unable to package my embedded webapp in such a way that this issue gets resolved. I am new to maven and packaging. Kindly Help where I am committing mistake.

推荐答案

如果您在MOXy jar中查看，则会看到文件夹META-INF/services.在该文件夹中，您将看到一个名为org.glassfish.jersey.internal.spi.AutoDiscoverable的文件.该文件的内容应为一行

If you look inside the MOXy jar, you will see a folder META-INF/services. In that folder, you will see a file named org.glassfish.jersey.internal.spi.AutoDiscoverable. The content of that file should be a single line

org.glassfish.jersey.moxy.json.internal.MoxyJsonAutoDiscoverable

此文件的作用是让Jersey发现MoxyJsonAutoDiscoverable，该MoxyJsonAutoDiscoverable将MOXy注册为Jersey.这种服务加载程序模式使Jersey可以发现功能并进行注册，而无需我们自己注册.

What this file is for is to allow Jersey to discover the MoxyJsonAutoDiscoverable, which registers MOXy for Jersey. This service loader pattern allows Jersey to discover features and register them, without us having to register them ourselves.

创建uber jar时出现的问题是，可能有多个jar包含相同的文件，因为不同的jar具有不同的发现功能，但是文件的名称必须与服务加载程序模式的确切名称相同有效.

The problem this poses when creating an uber jar is that there may be multiple jars with the same file, as different jars have different features to discover, but the file needs to be that exact name as that is how the service loader pattern works.

因此，您有一堆具有相同文件的jar，但是在创建uber jar时，不能有多个具有相同名称的文件.只是不可能.因此，只有一个文件被放入最终的jar中.哪一个..谁知道.但这意味着，如果MOXy的文件不是一个文件，则不会自动发现其功能，因此我们需要自己注册.因此，这些类被打包在uber jar中，但是主要功能部件只是未注册.您可以自己注册

So you have a bunch of jars with the same file, but when you create the uber jar, you cannot have multiple files with the same name. It's just not possible. So only one of the files gets put into the final jar. Which one.. who knows. But that means that if MOXy's files is not that one file then its feature will not be auto-discovered, and we need to register it ourselves. So the classes are packaged in the uber jar, but the main feature component is just not registered. You could just register it yourself

jerseyServlet.setInitParameter("jersey.config.server.provider.classnames",
                               "org.glassfish.jersey.moxy.json.MoxyJsonFeature");

但是由于未包含其自动发现文件而可能遗漏的所有其他可能功能又如何呢?

but what about all the other possible features that are possibly left out because their auto-discoverable file is not included?

因此，您应该使用 ，它具有允许我们将服务文件的内容连接到一个文件中的转换器.

For this reason, instead of the assembly plugin, you should use the maven-shade-plugin, which has transformers that allow us to concatenate the contents of service files into one file.

配置看起来像

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-shade-plugin</artifactId>
    <version>2.3</version>
    <configuration>
        <createDependencyReducedPom>true</createDependencyReducedPom>
        <filters>
            <filter>
                <artifact>*:*</artifact>
                <excludes>
                    <exclude>META-INF/*.SF</exclude>
                    <exclude>META-INF/*.DSA</exclude>
                    <exclude>META-INF/*.RSA</exclude>
                </excludes>
            </filter>
        </filters>
    </configuration>
    <executions>
        <execution>
            <phase>package</phase>
            <goals>
                <goal>shade</goal>
            </goals>
            <configuration>
                <transformers>
                    <transformer implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"/>
                    <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                        <mainClass>com.example.YourApp</mainClass>
                    </transformer>
                </transformers>
            </configuration>
        </execution>
    </executions>
</plugin>

ServicesResorceTransformaer是连接文件的文件.该插件的特定配置来自 Dropwizard入门.您可能需要检查一下以获取进一步的解释.

The ServicesResorceTransformaer is what concatenates the files. This particular configuration of the plugin was taking from the Dropwizard getting started. You may want to check that out for further explanation.

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