Question

我添加了具有这种依赖关系的库

        <dependency>
            <groupId>org.codehaus.jackson</groupId>
            <artifactId>jackson-core-asl</artifactId>
            <version>1.9.13</version>
        </dependency>
        <dependency>
            <groupId>org.codehaus.jackson</groupId>
            <artifactId>jackson-mapper-asl</artifactId>
            <version>1.9.13</version>
        </dependency>

然后当我尝试创建pojo类时，Idea告诉我找不到类，但是类存在 java.lang.ClassNotFoundException：org.codehaus.jackson.annotate.JsonUnwrapped

@Override
public void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    resp.addHeader("Content-Type", "application/json; charset=utf-8");
    StringBuilder builder = new StringBuilder();
    String a = null;
    try (BufferedReader reader = new BufferedReader(new InputStreamReader(req.getInputStream(), "UTF-8"))){
        while ((a = reader.readLine())!=null){
            builder.append(a);
        }
    }
    ObjectMapper objectMapper = new ObjectMapper();
    UserPojo pojo = objectMapper.readValue(builder.toString(),UserPojo.class);
   }

示例图片：

我在类路径中有这个库。我尝试使用其他版本的杰克逊。当我使用版本2. +时，我遇到另一个疯狂的错误提示Idea只能在此类中找不到ObjectMapper类。

在这张照片上，我有未找到类（ObjectMapper）的错误：

在这张照片上我没有错误：

但是这两个类放在一个包中。怎么可能和如何解决？

添加pom

<?xml version="1.0" encoding="UTF-8"?>
<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>PetClinic</groupId>
    <artifactId>cpw</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>war</packaging>

    <name>Clinic Pet Web</name>
    <url>http://maven.apache.org</url>

    <dependencies>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>5.3.5.Final</version>
        </dependency>
        <dependency>
            <groupId>postgresql</groupId>
            <artifactId>postgresql</artifactId>
            <version>9.1-901-1.jdbc4</version>
        </dependency>
        <dependency>
            <groupId>org.codehaus.jackson</groupId>
            <artifactId>jackson-core-asl</artifactId>
            <version>1.9.13</version>
        </dependency>
        <dependency>
            <groupId>org.codehaus.jackson</groupId>
            <artifactId>jackson-mapper-asl</artifactId>
            <version>1.9.13</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <dependency>
            <groupId>jstl</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <version>2.5</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>commons-logging</groupId>
            <artifactId>commons-logging</artifactId>
            <version>1.1.1</version>
        </dependency>
        <dependency>
            <groupId>taglibs</groupId>
            <artifactId>standard</artifactId>
            <version>1.1.2</version>
        </dependency>
        <dependency>
            <groupId>commons-lang</groupId>
            <artifactId>commons-lang</artifactId>
            <version>2.1</version>
        </dependency>
        <dependency>
            <groupId>org.codehaus.plexus</groupId>
            <artifactId>plexus-utils</artifactId>
            <version>1.1</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.8.2</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>PetClinic</groupId>
            <artifactId>se</artifactId>
            <version>1.0-SNAPSHOT</version>
        </dependency>
        <dependency>
            <groupId>org.mockito</groupId>
            <artifactId>mockito-all</artifactId>
            <version>1.10.19</version>
            <scope>test</scope>
        </dependency>

    </dependencies>

    <build>
        <finalName>PetClinicWeb</finalName>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.3</version>
                <configuration>
                    <source>1.7</source>
                    <target>1.7</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.jacoco</groupId>
                <artifactId>jacoco-maven-plugin</artifactId>
                <version>0.7.4.201502262128</version>
                <configuration>
                    <destFile>${basedir}/target/coverage-reports/jacoco-unit.exec</destFile>
                    <dataFile>${basedir}/target/coverage-reports/jacoco-unit.exec</dataFile>
                </configuration>
                <executions>
                    <execution>
                        <id>jacoco-initialize</id>
                        <goals>
                            <goal>prepare-agent</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>jacoco-site</id>
                        <phase>package</phase>
                        <goals>
                            <goal>report</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

Answer 1

尝试使用com.fasterxml jackson-annotations和jackson-core程序包，通常最好使用2+版本。好像您拥有的类JsonUnwrapped来自org.codehaus.jackson包中的版本1，而其他一些库则使用版本2（具有不同的包com.fasterxml.jackson）。尝试将您的杰克逊依赖项替换为以下内容：

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <PropertyGroup>
    <OutputPath>R:\VisualStudioBuilds\$(AssemblyName)\bin\$(Configuration)\</OutputPath>
  </PropertyGroup>
</Project>

至于缺少ObjectMapper，很可能您没有更新导入语句。因此，切换到版本2，并用fasterxml替换所有导入的Codehouse Jackson。所有杰克逊库都必须具有相同版本。

如果您的项目中有任何父项目，请检查是否在其中导入了jackson以及它的版本。它可能具有较旧的版本，在这种情况下，请分别更改您的库版本，或者只是删除该版本，以使其从父级继承。

有关更多详细信息，请参见https://dzone.com/articles/jackson-dependency-issue-in-spring-boot-with-maven

Answer 2

我要添加杰克逊2.7.8版

<dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-annotations</artifactId>
        <version>2.7.8</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-core</artifactId>
        <version>2.7.8</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.7.8</version>
    </dependency>

比起在Maven Project中进行清洁和打包

But ObjectMapper is not found

<?xml version="1.0" encoding="UTF-8"?>
<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>PetClinic</groupId>
    <artifactId>PetClinicMain</artifactId>
    <version>1.0-SNAPSHOT</version>

    <packaging>pom</packaging>

    <name>Pet Clinic</name>
    <url>http://maven.apache.org</url>

    <modules>
        <module>se</module>
        <module>clinic-pet-web</module>
    </modules>

</project>

Answer 3

我已经固定好了这个例外。我将杰克逊jar文件添加到WEB-INF / lib 正如我所理解的那样，添加依赖不够。 enter image description here

java.lang.ClassNotFoundException这怎么可能？

3 个答案: