导入 com.fasterxml.jackson.databind.ObjectMapper 无法解析

Posted 2023-02-15

【中文标题】导入 com.fasterxml.jackson.databind.ObjectMapper 无法解析

【英文标题】：The import com.fasterxml.jackson.databind.ObjectMapper cannot be resolved

【发布时间】：2018-10-18 14:27:38

【问题描述】：

我正在尝试创建一个 JSON 文件，但在尝试使用 ObjectMapper 类时遇到了问题。这是我的课程代码：

import java.math.BigDecimal;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import desafiodimensiva.entities.Desafio2;

@RestController
public class Desafio2Controller 

    @RequestMapping(value = "/teste")
    public String index() 
        return "Greetings from Spring Boot!";
    
    @RequestMapping("/desafio2")
    public Desafio2 novoDesafio2() 
        ObjectMapper mapper = new ObjectMapper();

        Desafio2 pessoa = new Desafio2();
        BigDecimal valorFinanceiroPessoa = new BigDecimal("0.00");
        pessoa.setNomePessoa("-----------                            ");
        pessoa.setIdPessoa("0000");
        pessoa.setValorFinanceiro(valorFinanceiroPessoa);

        return pessoa;
    

还有我的 pom.xml ：

`<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>com.desafio.dimensiva</groupId>
    <artifactId>desafiodimensiva</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>war</packaging>
    <name>Desafio Dimensiva</name>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.0.BUILD-SNAPSHOT</version>
    </parent>

    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.apache.tomcat</groupId>
            <artifactId>tomcat</artifactId>
            <version>8.5.0</version>
            <type>pom</type>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>5.2.6.Final</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>5.2.6.Final</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.22</version>
        </dependency>
        <dependency>
            <groupId>com.mchange</groupId>
            <artifactId>c3p0</artifactId>
            <version>0.9.5-pre3</version>
        </dependency>
        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.4</version>
        </dependency>


        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.9.0</version>
        </dependency>

    </dependencies>

    <build>
        <finalName>desafiodimensiva</finalName>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <executable>true</executable>
                </configuration>
            </plugin>

        </plugins>
    </build>


    <repositories>
        <repository>
            <id>spring-snapshots</id>
            <url>https://repo.spring.io/snapshot</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </repository>
        <repository>
            <id>spring-milestones</id>
            <url>https://repo.spring.io/milestone</url>
        </repository>
    </repositories>
    <pluginRepositories>
        <pluginRepository>
            <id>spring-snapshots</id>
            <url>https://repo.spring.io/snapshot</url>
        </pluginRepository>
        <pluginRepository>
            <id>spring-milestones</id>
            <url>https://repo.spring.io/milestone</url>
        </pluginRepository>
    </pluginRepositories>



</project>`

即使在 pom.xml 文件中添加了 jackson-databind 依赖项，我也无法导入 ObjectMapper 类。并且 jars jackson-annotations-2.9.0.jar, jackson-core-2.9.5.jar, jackson-databind-2.9.0.jar 在类路径中。

【问题讨论】：

删除这个依赖...检查你的依赖树mvn dependency:tree，你会发现多个...它带有spring boot starter web，尤其是你正在使用的版本！

试试mvn dependency:purge-local-repository。这应该可以清理所有内容并可能解决问题。

【参考方案1】：

删除jackson依赖jackson-databind的版本，即直接写

   <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
    </dependency>

在您的pom.xml 中。让 spring-boot 为你决定版本。

随意从类路径中删除 jars。

【讨论】：

请提及 pom.xml 文件的位置

【参考方案2】：

删除

 <dependency>                                         
    <groupId>com.fasterxml.jackson.core</groupId>    
    <artifactId>jackson-databind</artifactId>        
    <version>2.9.0</version> <--- remove this
 </dependency>                                        

如果您在 intellij Maven > Show Effective POM 上，还可以通过右键单击 pom.xml 来查看有效的 pom。检查那里的冲突。

 <dependency>                                         
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>    
 </dependency>                                        

然后试试

 mvn dependency:purge-local-repository;

这将首先解析整个依赖树，然后从本地存储库中删除内容，然后从远程存储库中重新解析依赖项。