Hibernate Validator参数校验

日常开发中经常会遇到需要参数校验的情况，比如某个字段不能为空、长度不能超过5等都属于参数校验的范围。对于简单的参数校验通过写几个if-else判断语句就搞定，但是对于复杂的多个参数校验的情况，就不是那么简单了，通常是各种循环嵌套+一堆if-else语句。一个字，丑！

所以，这就需要引进本文的主人公——Hibernate Validator（下文简称hb）。顾名思义，这是出自ORM框架Hibernate之手，那么，这个玩意可以帮助我们什么呢？

Express validation rules in a standardized way using annotation-based constraints and benefit from transparent integration with a wide variety of frameworks.

使用基于注解的约束，以标准化的方式表达验证规则，并可以与大多数框架无缝集成。

既然是基于注解进行阐述校验，那么有哪些注解呢？

参数注解

hv的参数校验有多个级别：

bean

method

bean也就是JavaBean（一个标准的）校验又有三种：

field constraints（字段）

property constraints（属性）

class constraints（类）

参数注解可以附加到字段、getter方法，类或者接口上面。对于一些特定的需求，用户可以很容易的开发定制化的约束。

hv提供了JSR规范中所有内置constraint的实现，除此之外还有一些附加的constraint。

快速入门

引入pom依赖：

<dependency>
<groupId>javax.validation</groupId>
<artifactId>validation-api</artifactId>
</dependency>

<dependency>
<groupId>org.glassfish</groupId>
<artifactId>javax.el</artifactId>
<version>3.0.1-b08</version>
</dependency>

<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-validator</artifactId>
<version>5.3.4.Final</version>
</dependency>

JavaBean:

public class CarBO {

@NotNull
private String manufacturer;

@NotNull
@Size(min = 2, max = 5)
private String licensePlate;

@Min(5)
private int seatCount;

public CarBO(String manufacturer, String licencePlate, int seatCount) {
this.manufacturer = manufacturer;
this.licensePlate = licencePlate;
this.seatCount = seatCount;
}

//setter、getter
}

编写测试类：

public class CarTest {
private static Validator validator;

@BeforeClass
public static void setUp() {
ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
validator = factory.getValidator();
}

@Test
public void manufacturerIsNull() {
CarBO car = new CarBO( null, "DD-AB-123", 4 );

Set<ConstraintViolation<CarBO>> constraintViolations =
validator.validate( car );

assertEquals( 1, constraintViolations.size() );
assertEquals(
"may not be null",
constraintViolations.iterator().next().getMessage()
);
}

@Test
public void licensePlateTooShort() {
CarBO car = new CarBO( "Morris", "D", 4 );

Set<ConstraintViolation<CarBO>> constraintViolations =
validator.validate( car );

assertEquals( 1, constraintViolations.size() );
assertEquals(
"size must be between 2 and 14",
constraintViolations.iterator().next().getMessage()
);
}

@Test
public void seatCountTooLow() {
CarBO car = new CarBO( "Morris", "DD-AB-123", 1 );

Set<ConstraintViolation<CarBO>> constraintViolations =
validator.validate( car );

assertEquals( 1, constraintViolations.size() );
assertEquals(
"must be greater than or equal to 2",
constraintViolations.iterator().next().getMessage()
);
}

@Test
public void carIsValid() {
CarBO car = new CarBO( "Morris", "DD-AB-123", 2 );

Set<ConstraintViolation<CarBO>> constraintViolations =
validator.validate( car );

assertEquals( 0, constraintViolations.size() );
}

}

在实际场景中，对于非法的参数需要抛出异常，比如哪个参数因为什么校验不通过。具体哪个字段可以通过ConstraintViolation的getPropertyPath方法获取，校验的提示信息可以通过ConstraintViolation的getMessage方法获取。

实例如下：

private void validate(CarBO car) {
Set<ConstraintViolation<CarBO>> constraintViolations = validator.validate( car );
if (!constraintViolations.isEmpty()) {
throw new RuntimeException("参数非法！！" + getValidateMsg(constraintViolations));
}
}

private String getValidateMsg(Set<ConstraintViolation<CarBO>> constraintViolations) {
StringBuilder msg = new StringBuilder();
for (ConstraintViolation<CarBO> violation : constraintViolations) {
msg.append(violation.getPropertyPath())
.append(violation.getMessage())
.append(",");
}
return msg.substring(0, msg.lastIndexOf(","));
}