Jackson writeValue 无法解析

Question

我想为 json 文件构建一个插入 JSON 对象，但我收到的消息是

Cannot resolve method writeValue(java.net.URL, object);

这是我的函数：

 @PostMapping("/insertBook")
    public void insertBook(@RequestBody Book book)  {
            objectMapper.writeValue(this.getClass().getResource("/books.json"),book);// this is the line couldn't resolve
        }

这是我的 pom.xml 文件：

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.4.5</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.visma</groupId>
    <artifactId>assigment</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>assigment</name>
    <description></description>
    <properties>
        <java.version>11</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>2.12.3</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.12.3</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

我最近开始使用 jackson ，也许我遗漏了什么？我正在关注此文档：https://github.com/FasterXML/jackson-databind#1-minute-tutorial-pojos-to-json-and-back

Answer 1

您应该将路径传递给文件本身，而不是 URL。

尝试这样的事情：

@PostMapping("/insertBook")
public void insertBook(@RequestBody Book book)  {
    File booksJsonFile = Paths.get(this.getClass().getResource("/books.json").toURI()).toFile();
    objectMapper.writeValue(booksJsonFile, book);
}

Jackson writeValue 无法解析

Jackson writeValue cannot be resolved

java

json

jackson

maven

spring-boot