优雅的参数验证——javax.validation

1.相关环境

1.基本环境
jdk 1.8
maven 3.2.5
springboot 2.1.5.RELEASE

2.相关依赖
 	<!--lombok-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <scope>provided</scope>
        </dependency>
        <!--hutool-->
        <dependency>
            <groupId>cn.hutool</groupId>
            <artifactId>hutool-core</artifactId>
            <version>5.0.6</version>
        </dependency>

2.使用

1.基本使用——内置注解

例如：在我们接受前台的参数时候，可以使用javax.validation进行校验，只需要打上对应的注解就可以完成基本的验证

public class TestDto {
    @NotBlank(message = "{user.register.username.not-blank}")
    private String userName;
}

拓展：将对应的非法内容统一放置到对应的ValidationMessages.properties，
位置为src/main/resources下
注意：中文乱码需要将properties的编码设置为UTF-8，在yml设置

spring:
  messages:
    encoding: UTF-8

例如

user.register.username.not-blank=用户名不可为空

2.拓展使用---自定义注解

我们需要根据自己的业务拓展不同的validtor,简化臃肿的代码
例如：判断两个字符串是否相同

1.自定义注解

定义验证所用的注解


import life.xp.jinglongeat.common.validator.impl.EqualFiledValidator;

import javax.validation.Constraint;
import javax.validation.Payload;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.ElementType.PARAMETER;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

/**
 * @Author xp
 * @Description 自定义验证字符串是否相同----用于校验前台内容的一致性
 * @Date 14:21 2020/2/15
 * @Param
 * @return
 **/
@Target({TYPE, METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER})
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = {EqualFiledValidator.class})
public @interface EqualField {
    /**源字段*/
    String srcField() default "";
    // dstField = "confirmPassword",
    /**目标字段*/
    String dstField() default "";
    // message = "{password.equal-field}"
    String message() default "the two fields must be equal";

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

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

2.对应实现

使用了反射去拿到对应的字段进行校验


import life.xp.jinglongeat.common.validator.EqualField;
import org.springframework.util.ReflectionUtils;

import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
import java.lang.reflect.Field;

/**
 * @ClassName: EqualFiledValidator
 * @Description: 自定义注解实现
 * @author: XP
 * @data: 2020/2/15
 */
public class EqualFiledValidator implements ConstraintValidator<EqualField, Object> {
    /**源字段*/
    private String srcField;
    /**目标字段*/
    private String dstField;
    @Override
    public void initialize(EqualField constraintAnnotation) {
        this.srcField=constraintAnnotation.srcField();
        this.dstField=constraintAnnotation.dstField();
    }

    @Override
    public boolean isValid(Object o, ConstraintValidatorContext constraintValidatorContext) {
        //1.拿到当前对象--dto
        Class<?> aClass = o.getClass();
        //拿到对应的字段
        Field srcField = ReflectionUtils.findField(aClass, this.srcField);
        Field dstField = ReflectionUtils.findField(aClass, this.dstField);

        try {
            srcField.setAccessible(true);
            dstField.setAccessible(true);
            //方法返回指定对象上由此Field表示的字段的值
            String src=(String)srcField.get(o);
            String dst=(String)dstField.get(o);
            //拿到对象的值 进行相同判断
            if(src.equals(dst)){
                return true;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return false;
    }
}

3.使用


/**
 * @ClassName: TestDto
 * @Description: 测试validator
 * @author: XP
 * @data: 2020/2/15
 */
@NoArgsConstructor
@Getter
@Setter
@EqualField(srcField = "password", dstField = "confirmPassword", message = "{password.equal-field}")
public class TestDto {
    @NotBlank(message = "{user.register.username.not-blank}")
    private String userName;
    @NotBlank(message = "{password.new-password.not-blank}")
    private String password;
    @NotBlank(message = "{password.confirm-password.not-blank}")
    private String confirmPassword;
}

3.原理

例如分析@NotBlank的源码

/*
 * Bean Validation API
 *
 * License: Apache License, Version 2.0
 * See the license.txt file in the root directory or <http://www.apache.org/licenses/LICENSE-2.0>.
 */
package javax.validation.constraints;

import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
import static java.lang.annotation.ElementType.CONSTRUCTOR;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.PARAMETER;
import static java.lang.annotation.ElementType.TYPE_USE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

import java.lang.annotation.Documented;
import java.lang.annotation.Repeatable;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import javax.validation.Constraint;
import javax.validation.Payload;
import javax.validation.constraints.NotBlank.List;

/**
 * The annotated element must not be {@code null} and must contain at least one
 * non-whitespace character. Accepts {@code CharSequence}.
 *
 * @author Hardy Ferentschik
 * @since 2.0
 *
 * @see Character#isWhitespace(char)
 */
@Documented
@Constraint(validatedBy = { })
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER, TYPE_USE })
@Retention(RUNTIME)
@Repeatable(List.class)
public @interface NotBlank {
	//内置相关验证说明
	String message() default "{javax.validation.constraints.NotBlank.message}";

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

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

	/**
	 * Defines several {@code @NotBlank} constraints on the same element.
	 *
	 * @see NotBlank
	 */
	@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER, TYPE_USE })
	@Retention(RUNTIME)
	@Documented
	public @interface List {
		NotBlank[] value();
	}
}

个人理解：在javax.validation.constraints包里面并没有实现相关的validator,提供了ValidatorFactory接口