SprinBoot集成参数校验Validator，以及参数校验的高阶技巧。

Validator校验框架遵循了JSR-303验证规范（参数校验规范）, JSR是Java Specification Requests的缩写。

在接口开发中，为了防止非法参数对业务造成影响，需要对接口的参数做校验，例如登录的时候需要校验用户名密码是否为空，靠代码对接口参数校验太繁琐了，代码可读性极差。

Hibernate Validator (jboss.org)

引入依赖

springboot-2.3之前的版本只需要引入 web 依赖

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

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

定义要参数校验的实体类

public class UserVO {

    private String userId;

    @Length(max = 12,message = "name长度必须小于12")
    private String name;

    private Integer age;

    private String sex;

    public String getUserId() {
        return userId;
    }

    public void setUserId(String userId) {
        this.userId = userId;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

}

自定义参数校验

有一些特殊场景，Spring Validation 提供的注解不适用，需要定制校验规则，如sex性别，只允许 M，WM 这2个枚举值

创建自定义注解

@Target({METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER, TYPE_USE})
@Retention(RUNTIME)
@Repeatable(EnumString.List.class)
@Documented
@Constraint(validatedBy = EnumStringValidator.class)//指定EnumStringValidator执行校验逻辑
public @interface EnumString {
    String message() default "value not in enum values.";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};

    //返回数据必须在此值数组中
    String[] value();

    /**
     * 在同一元素上定义多个{@link EnumString}注解。
     */
    @Target({METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER, TYPE_USE})
    @Retention(RUNTIME)
    @Documented
    @interface List {
        EnumString[] value();
    }

}

自定义校验逻辑

public class EnumStringValidator implements ConstraintValidator<EnumString, String> {
    private List<String> enumStringList;

    @Override
    public void initialize(EnumString constraintAnnotation) {
        enumStringList = Arrays.asList(constraintAnnotation.value());
    }

    @Override
    public boolean isValid(String value, ConstraintValidatorContext context) {
        if(value == null){
            return true;
        }
        return enumStringList.contains(value);
    }
}

在校验对象的属性上加上注解

public class UserVO {

    private String userId;

    @Length(max = 12,message = "name长度必须小于12")
    private String name;

    private Integer age;

    @EnumString(value = {"M","WM"}, message="性别只允许为M或WM")
    private String sex;

    public String getUserId() {
        return userId;
    }

    public void setUserId(String userId) {
        this.userId = userId;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

}

分组校验

在不同的场景，校验规则也不一样，如新增不需要userId，查询、修改、删除需要userId。为避免建立多个VO校验对象，可以使用分组校验

定义分组接口

定义一个分组接口ValidGroup继承javax.validation.groups.Default，再在分组接口中定义出多个不同的操作类型，Create，Update，Query，Delete。

public interface ValidGroup extends Default {

    interface Crud extends ValidGroup{
        interface Create extends Crud{

        }

        interface Update extends Crud{

        }

        interface Query extends Crud{

        }

        interface Delete extends Crud{

        }
    }
}

在UserVO对象参数分配分组

public class UserVO {

    @Null(groups = ValidGroup.Crud.Create.class)
    @NotNull(groups = {ValidGroup.Crud.Query.class, ValidGroup.Crud.Update.class}, message = "userId不能为空")
    private String userId;

    @Length(max = 12,message = "name长度必须小于12")
    private String name;

    private Integer age;

    @EnumString(value = {"M","WM"}, message="性别只允许为M或WM")
    private String sex;

    public String getUserId() {
        return userId;
    }

    public void setUserId(String userId) {
        this.userId = userId;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    @Override
    public String toString() {
        return "UserVO{" +
                "userId='" + userId + '\'' +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", sex='" + sex + '\'' +
                '}';
    }
}

在需要参数校验的方法指定分组

@RestController
public class UserController {

    /**
     * Form新增校验
     * @param userVO
     * @return
     */
    @PostMapping(value = "/user/add")
    public String add(@Validated(value = ValidGroup.Crud.Create.class) UserVO userVO){
        System.out.println("add " + userVO);
        return "add valid success";
    }

    /**
     * 查询
     * @param userVO
     * @return
     */
    @GetMapping(value = "/user/query")
    public String query(@Validated(value = ValidGroup.Crud.Query.class) UserVO userVO){
        System.out.println("query " + userVO);
        return "query valid success";
    }

    /**
     * json更新
     * @param userVO
     * @return
     */
    @PutMapping(value = "/user/update")
    public String update(@Validated(value = ValidGroup.Crud.Update.class) @RequestBody UserVO userVO){
        System.out.println("update " + userVO);
        return "update valid success";
    }

    /**
     * 删除
     * @param userId
     * @return
     */
    @DeleteMapping(value = "/user/del")
    public String del(@NotBlank String userId){
        System.out.println("del "+ userId);
        return "del valid success";
    }

}