Maven 构建失败，"package com.fasterxml.jackson does not exist"

Question

我需要在我的maven项目中解析一个json文件。为此，我从java文件(App.java)中的一个简单导入开始

package com.mycompany.app;
import com.fasterxml.jackson.*;// <-------- HERE
public class App
{
public static void main( String[] args )
{
}
}

然后，我尝试使用mvn package编译该项目，但我得到了一个错误：

[INFO] Scanning for projects...
[INFO] 
[INFO] ----------------------< com.mycompany.app:my-app >----------------------
[INFO] Building my-app 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO] 
[INFO] --- maven-resources-plugin:3.0.2:resources (default-resources) @ my-app ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory /tmp/my-app/src/main/resources
[INFO] 
[INFO] --- maven-compiler-plugin:3.8.0:compile (default-compile) @ my-app ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 1 source file to /tmp/my-app/target/classes
[INFO] -------------------------------------------------------------
[ERROR] COMPILATION ERROR : 
[INFO] -------------------------------------------------------------
[ERROR] /tmp/my-app/src/main/java/com/mycompany/app/App.java:[2,1] package com.fasterxml.jackson does not exist
[INFO] 1 error
[INFO] -------------------------------------------------------------
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  0.628 s
[INFO] Finished at: 2022-05-10T15:31:39+02:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.0:compile (default-compile) on project my-app: Compilation failure
[ERROR] /tmp/my-app/src/main/java/com/mycompany/app/App.java:[2,1] package com.fasterxml.jackson does not exist
[ERROR] 
[ERROR] -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException

以下是我如何构建我的maven项目：

1. 我创建了我的maven项目：

mvn -B archetype:generate -DgroupId=com.mycompany.app -DartifactId=my-app -DarchetypeArtifactId=maven-archetype-quickstart -DarchetypeVersion=1.4

2. 我修改了文件App.java(由上一个命令创建)以与我的文件匹配
3. 我修改了pom.xml以添加依赖项：

<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-core -->
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.13.2</version>
</dependency>

你知道如何解决这个错误吗？

Answer 1

我最近已经回答了一个类似的问题：问题是com.fasterxml.jackson不是一个包，有一个文件夹com/fasterxml/jackson(请参阅源代码)，但不是包。在Java中，package是一个至少包含一个类的命名空间。Asterix import以非递归方式导入包中的所有类。因此，如果您需要，比如说，使用包com.fasterxml.jackson.core中的类JsonParser.java和JacksonException.java，您可以添加一个类似的asterix导入：com.fasterxml.jackson.core.*