Spring Boot @Size验证失效求助：Postman测试接口不生效

测试http://localhost:8080/departments POST接口时，发现实体类Department的departmentName字段标注的@Size(min = 2)和@NotBlank验证规则未生效：

• 传入departmentName为"a"的JSON数据，接口正常执行
• 删除departmentName字段后，接口依然正常工作

相关代码如下：

实体类代码 #

package com.dailycodebuffer.Springboottutorial.entity;

import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

import javax.validation.constraints.NotBlank;
import javax.validation.constraints.Size;

@Entity
@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class Department {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long departmentId;
    @NotBlank(message = "Please add Department Name")
    @Size(min = 2, message = "Department Name must be at least 2 characters long")
    private String departmentName;
    private String departmentAdress;
    private String departmentCode;
}

控制器代码 #

package com.dailycodebuffer.Springboottutorial.controller;

import com.dailycodebuffer.Springboottutorial.entity.Department;
import com.dailycodebuffer.Springboottutorial.error.DepartmentNotFoundException;
import com.dailycodebuffer.Springboottutorial.service.DepartmentService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.*;

import javax.validation.Valid;
import java.util.List;
import java.util.Optional;

@RestController
@Validated
public class DepartmentController {

    @Autowired
    private DepartmentService departmentService;

    private final Logger LOGGER = LoggerFactory.getLogger(DepartmentController.class);

    @PostMapping("/departments")
    public Department saveDepartment(@Valid @RequestBody Department department) {
        LOGGER.info("Inside saveDepartment of DepartmentController");
        return departmentService.saveDepartment(department);
    }

    @GetMapping("/departments")
    public List<Department> fetchDepartmentList() {
        LOGGER.info("Inside fetchDepartment of DepartmentController");
        return departmentService.fetchDepartmentList();
    }

    @GetMapping("/departments/{departmentId}")
    public Optional<Department> fetchDepartmentById(@PathVariable Long departmentId) throws DepartmentNotFoundException {
        return departmentService.fetchDepartmentById(departmentId);
    }

    @DeleteMapping("/departments/{departmentId}")
    public String deleteDepartmentById(@PathVariable Long departmentId) {
        departmentService.deleteDepartmentById(departmentId);
        return "Succes";
    }

    @PutMapping("/departments/{departmentId}")
    public Department updateDepartment(@PathVariable Long departmentId, @RequestBody Department department) {
        return departmentService.updateDepartment(departmentId, department);
    }

    @GetMapping("/departments/name/{departmentName}")
    public Department fetchDepartmentByName(@PathVariable String departmentName) {
        return departmentService.fetchDepartmentByName(departmentName);
    }

}

pom.xml配置 #

<?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>3.1.3</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <groupId>com.dailycodebuffer</groupId>
    <artifactId>Spring-boot-tutorial</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>Spring-boot-tutorial</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>20</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</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-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>javax.validation</groupId>
            <artifactId>validation-api</artifactId>
            <version>2.0.1.Final</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.28</version>
        </dependency>
    </dependencies>

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

</project>

原因分析及解决方案 #

1. 依赖包版本与Spring Boot 3.x不兼容 #

Spring Boot 3.x基于Jakarta EE 9规范，当前pom.xml中引入的是旧Java EE规范的javax.validation:validation-api，该包的注解无法被Spring Boot 3.x的验证引擎识别。

解决方案：

• 删除pom.xml中的javax.validation:validation-api依赖
• 添加Spring Boot官方提供的validation starter依赖，它会自动引入兼容Jakarta EE的验证包：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-validation</artifactId>
</dependency>

2. 实体类注解导入错误 #

实体类中使用的是javax.validation.constraints下的注解，而Spring Boot 3.x只识别jakarta.validation.constraints下的Jakarta版本注解，导致验证规则不生效。

解决方案：
修改实体类中的注解导入路径，替换为Jakarta版本：

import jakarta.validation.constraints.NotBlank;
import jakarta.validation.constraints.Size;

3. （可选）添加全局异常处理器优化错误返回 #

验证生效后，Spring Boot会默认返回400状态码，但错误信息不够直观。添加全局异常处理器可以捕获验证异常，返回友好的字段错误提示。

解决方案：
创建全局异常处理类：

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.validation.FieldError;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;

import java.util.HashMap;
import java.util.Map;

@RestControllerAdvice
public class GlobalValidationExceptionHandler {

    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResponseEntity<Map<String, String>> handleValidationErrors(MethodArgumentNotValidException ex) {
        Map<String, String> errorMap = new HashMap<>();
        ex.getBindingResult().getAllErrors().forEach(error -> {
            String fieldName = ((FieldError) error).getField();
            String errorMessage = error.getDefaultMessage();
            errorMap.put(fieldName, errorMessage);
        });
        return new ResponseEntity<>(errorMap, HttpStatus.BAD_REQUEST);
    }
}

内容的提问来源于stack exchange，提问作者GPPiotr