Java Spring引导Rest控制器错误，正在使用Jackson和Hibernate将POJO转换为JSON

所以这个问题被问了好几次，我在So和其他问题网站上看到了类似的答案。答案似乎总是要么将Jackson依赖项放在类路径中，要么确保POJO类具有公共getter（我已经尝试过了，但无法摆脱此错误消息）。我有一个连接到MySQL数据库的Spring Boot应用程序，我几乎没有配置，因为我想看看Spring Boot可以自动配置到什么程度。我在pom.xml中有两个spring启动启动程序，我想它们会处理依赖关系吗？当我测试请求路径时，我得到stacktrace

No converter found for return value of type: class com.portfolio.bork.webapp.model.Project
org.springframework.http.converter.HttpMessageNotWritableException: No converter found for return value of type: class com.portfolio.bork.webapp.model.Project
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:230)
    at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:181)
    at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:82)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:124)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:879)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:367)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1639)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)

控制台中的一条错误消息说

.w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.http.converter.HttpMessageNotWritableException: No converter found for return value of type: class com.portfolio.bork.webapp.model.Project]
.w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.http.converter.HttpMessageNotWritableException: No converter found for return value of type: class java.util.LinkedHashMap]

这是我的pom.xml

<?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>2.2.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.portfolio.bork</groupId>
    <artifactId>webapp</artifactId>
    <version>01</version>
    <packaging>war</packaging>
    <name>webapp</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <!-- <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions> -->
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <!-- <scope>runtime</scope> -->
        </dependency>

        <!-- for testing as of now -->
        <dependency>
            <groupId>org.apache.tomcat</groupId>
            <artifactId>tomcat-jdbc</artifactId>
            <version>8.5.27</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.10.3</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

父类Project.java

package com.portfolio.bork.webapp.model;

import java.util.List;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

@Entity
@Table (name = "project")
public class Project{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column (name = "p_id")
    private Long id;
    @Column( name="p_title" )
    private String title;
    @Column( name = "p_date_modified")
    private String dateModified;
    @OneToMany(mappedBy = "project")
    private List<ContentBlock> contentBlocks;

    public Project() {
    }


    public Project(Long id, String title, String dateModified, List<ContentBlock> contentBlocks) {
        this.id = id;
        this.title = title;
        this.dateModified = dateModified;
        this.contentBlocks = contentBlocks;
    }

    public Long getId() {
        return this.id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getTitle() {
        return this.title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDateModified() {
        return this.dateModified;
    }

    public void setDateModified(String dateModified) {
        this.dateModified = dateModified;
    }

    public List<ContentBlock> getContentBlocks() {
        return this.contentBlocks;
    }

    public void setContentBlocks(List<ContentBlock> contentBlocks) {
        this.contentBlocks = contentBlocks;
    }

    @Override
    public String toString() {
        return "{" +
            " id='" + getId() + "'" +
            ", title='" + getTitle() + "'" +
            ", dateModified='" + getDateModified() + "'" +
            "}";
    }


}

package com.portfolio.bork.webapp.model；
导入java.util.List；
导入javax.persistence.Column；
导入javax.persistence.Entity；
导入javax.persistence.GeneratedValue；
导入javax.persistence.GenerationType；
导入javax.persistence.Id；
导入javax.persistence.OneToMany；
导入javax.persistence.Table；
@实体
@表（name=“项目”）
公共类项目{
@身份证
@GeneratedValue（策略=GenerationType.IDENTITY）
@列（name=“p_id”）
私人长id；
@列（name=“p_title”）
私有字符串标题；
@列（name=“p\u日期\u修改”）
修改私有字符串；
@OneToMany（mappedBy=“项目”）
私有列表内容块；
公共工程（）{
}
公共项目（长id、字符串标题、字符串日期修改、列表内容块）{
this.id=id；
this.title=标题；
this.dateModified=dateModified；
this.contentBlocks=contentBlocks；
}
公共长getId（）{
返回此.id；
}
公共无效集合id（长id）{
this.id=id；
}
公共字符串getTitle（）{
返回此.title；
}
公共无效集合标题（字符串标题）{
this.title=标题；
}
公共字符串getDateModified（）{
返回此.dateModified；
}
public void setDateModified（字符串dateModified）{
this.dateModified=dateModified；
}
公共列表getContentBlocks（）{
返回此.contentBlocks；
}
公共void setContentBlocks（列出contentBlocks）{
this.contentBlocks=contentBlocks；
}
@凌驾
公共字符串toString（）{
返回“{”+
“id=”+getId（）+“”+
，title=“+getTitle（）+””+
，dateModified=“+getDateModified（）+””+
"}";
}
}

儿童班

package com.portfolio.bork.webapp.model;

import java.util.List;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

@Entity
@Table (name = "project")
public class Project{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column (name = "p_id")
    private Long id;
    @Column( name="p_title" )
    private String title;
    @Column( name = "p_date_modified")
    private String dateModified;
    @OneToMany(mappedBy = "project")
    private List<ContentBlock> contentBlocks;

    public Project() {
    }


    public Project(Long id, String title, String dateModified, List<ContentBlock> contentBlocks) {
        this.id = id;
        this.title = title;
        this.dateModified = dateModified;
        this.contentBlocks = contentBlocks;
    }

    public Long getId() {
        return this.id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getTitle() {
        return this.title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDateModified() {
        return this.dateModified;
    }

    public void setDateModified(String dateModified) {
        this.dateModified = dateModified;
    }

    public List<ContentBlock> getContentBlocks() {
        return this.contentBlocks;
    }

    public void setContentBlocks(List<ContentBlock> contentBlocks) {
        this.contentBlocks = contentBlocks;
    }

    @Override
    public String toString() {
        return "{" +
            " id='" + getId() + "'" +
            ", title='" + getTitle() + "'" +
            ", dateModified='" + getDateModified() + "'" +
            "}";
    }


}

package com.portfolio.bork.webapp.model；
导入java.util.List；
导入javax.persistence.Column；
导入javax.persistence.Entity；
导入javax.persistence.GeneratedValue；
导入javax.persistence.GenerationType；
导入javax.persistence.Id；
导入javax.persistence.OneToMany；
导入javax.persistence.Table；
@实体
@表（name=“项目”）
公共类项目{
@身份证
@GeneratedValue（策略=GenerationType.IDENTITY）
@列（name=“p_id”）
私人长id；
@列（name=“p_title”）
私有字符串标题；
@列（name=“p\u日期\u修改”）
修改私有字符串；
@OneToMany（mappedBy=“项目”）
私有列表内容块；
公共工程（）{
}
公共项目（长id、字符串标题、字符串日期修改、列表内容块）{
this.id=id；
this.title=标题；
this.dateModified=dateModified；
this.contentBlocks=contentBlocks；
}
公共长getId（）{
返回此.id；
}
公共无效集合id（长id）{
this.id=id；
}
公共字符串getTitle（）{
返回此.title；
}
公共无效集合标题（字符串标题）{
this.title=标题；
}
公共字符串getDateModified（）{
返回此.dateModified；
}
public void setDateModified（字符串dateModified）{
this.dateModified=dateModified；
}
公共列表getContentBlocks（）{
返回此.contentBlocks；
}
公共void setContentBlocks（列出contentBlocks）{
this.contentBlocks=contentBlocks；
}
@凌驾
公共字符串toString（）{
返回“{”+
“id=”+getId（）+“”+
，title=“+getTitle（）+””+
，dateModified=“+getDateModified（）+””+
"}";
}
}

您明确告诉Maven在运行应用程序时不要包含提供转换器的

jackson数据绑定，因为您说它只用于
测试。消除整个依赖关系<代码>spring boot starter web将自动包含它。
谢谢，我知道它必须是一些小东西
package com.portfolio.bork.webapp.model;

import java.util.List;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

@Entity
@Table (name = "project")
public class Project{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column (name = "p_id")
    private Long id;
    @Column( name="p_title" )
    private String title;
    @Column( name = "p_date_modified")
    private String dateModified;
    @OneToMany(mappedBy = "project")
    private List<ContentBlock> contentBlocks;

    public Project() {
    }


    public Project(Long id, String title, String dateModified, List<ContentBlock> contentBlocks) {
        this.id = id;
        this.title = title;
        this.dateModified = dateModified;
        this.contentBlocks = contentBlocks;
    }

    public Long getId() {
        return this.id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getTitle() {
        return this.title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDateModified() {
        return this.dateModified;
    }

    public void setDateModified(String dateModified) {
        this.dateModified = dateModified;
    }

    public List<ContentBlock> getContentBlocks() {
        return this.contentBlocks;
    }

    public void setContentBlocks(List<ContentBlock> contentBlocks) {
        this.contentBlocks = contentBlocks;
    }

    @Override
    public String toString() {
        return "{" +
            " id='" + getId() + "'" +
            ", title='" + getTitle() + "'" +
            ", dateModified='" + getDateModified() + "'" +
            "}";
    }


}