Spring Boot读取请求体失败，插入员工数据时字段为null报错

我是Java和Spring Boot新手，开发简单REST API插入员工记录到MySQL时遇到以下错误：

@RequestBody => Employee [id=0, firstName=null, lastName=null, email=null]
Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed: org.springframework.dao.DataIntegrityViolationException: not-null property references a null or transient value : com.saa.springboot.model.Employee.firstName] with root cause

org.hibernate.PropertyValueException: not-null property references a null or transient value : com.saa.springboot.model.Employee.firstName
    at org.hibernate.engine.internal.Nullability.checkNullability(Nullability.java:111) ~[hibernate-core-6.1.7.Final.jar:6.1.7.Final]

Employee实体类代码 #

@Data
@Entity
@Table(name="employees")
public class Employee {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;
    
    @Column(name = "first_name", nullable = false)
    private String firstName;
    
    @Column(name = "last_name")
    private String lastName;
    
    @Column(name = "email")
    private String email;
}

EmployeeController代码 #

package com.saa.springboot.controller;

import java.util.List;

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import com.saa.springboot.model.Employee;
import com.saa.springboot.service.EmployeeService;


@RestController
@RequestMapping("/api/employees")
public class EmployeeController {
    
    private EmployeeService employeeService;

    public EmployeeController(EmployeeService employeeService) {
        super();
        this.employeeService = employeeService;
    }
    
    @PostMapping()
    public ResponseEntity<Employee> saveEmployee(@RequestBody Employee employee) {
        System.out.println("@RequestBody => " + employee.toString());
        return new ResponseEntity<Employee>(employeeService.saveEmployee(employee), HttpStatus.CREATED);
    }
    
}

应用配置文件 #

spring.datasource.url = jdbc:mysql://localhost:3306/ems_db?useSSL=false
spring.datasource.username = root
spring.datasource.password = pwd
spring.jpa.database-platform = org.hibernate.dialect.MySQLDialect
spring.jpa.generate-ddl = true
spring.jpa.hibernate.ddl-auto = update

Curl请求 #

curl -i -H "Accept: application/json" -H "Content-Type:application/json" -X POST --data "{\"firstName\": \"john\", \"lastName\": \"cena\"}" "http://localhost:8080/api/employees"

从打印日志可以看到，@RequestBody读取的所有字段值都是null：

@RequestBody => Employee [id=0, firstName=null, lastName=null, email=null]

Postman测试也出现同样错误，求指导。

问题核心是Jackson无法为Employee实体类注入JSON属性值，导致所有字段为null，进而触发数据库非空约束报错。主要原因及解决办法如下：

1. 检查Lombok插件与依赖 #

你用了@Data注解自动生成getter/setter，但如果IDE未安装Lombok插件，或项目未引入Lombok依赖，编译后的实体类不会生成setter方法，Jackson无法设置属性值：

• 安装IDE Lombok插件：比如IntelliJ IDEA需在Settings > Plugins中搜索安装Lombok插件，重启IDE生效。
• 确认依赖配置：pom.xml中添加Lombok依赖：

  <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <optional>true</optional>
  </dependency>
  

  Gradle项目则添加：

  compileOnly 'org.projectlombok:lombok'
  annotationProcessor 'org.projectlombok:lombok'
  

2. 验证实体类的setter方法 #

编译项目后，查看target/classes（Maven）或build/classes（Gradle）下的Employee.class文件，确认是否存在setFirstName()、setLastName()等方法。若不存在，说明Lombok未生效，回到第一步排查。

3. 替代方案：手动添加getter/setter #

如果不想依赖Lombok，可直接在Employee类中手动编写getter和setter方法：

@Entity
@Table(name="employees")
public class Employee {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;
    
    @Column(name = "first_name", nullable = false)
    private String firstName;
    
    @Column(name = "last_name")
    private String lastName;
    
    @Column(name = "email")
    private String email;

    // Getters
    public long getId() { return id; }
    public String getFirstName() { return firstName; }
    public String getLastName() { return lastName; }
    public String getEmail() { return email; }

    // Setters
    public void setId(long id) { this.id = id; }
    public void setFirstName(String firstName) { this.firstName = firstName; }
    public void setLastName(String lastName) { this.lastName = lastName; }
    public void setEmail(String email) { this.email = email; }

    // 手动添加toString方法（可选）
    @Override
    public String toString() {
        return "Employee [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", email=" + email + "]";
    }
}

4. 确认JSON字段匹配 #

你的curl请求中firstName、lastName与实体类字段名完全匹配（大小写敏感），这部分无需调整。

内容的提问来源于stack exchange，提问作者Satishakumar Awati