边学边用,有问题欢迎指出。
Chapter 1. 简单的 Annotation Constraint 的使用
package tutorial.chapter01; import javax.validation.constraints.Min; import javax.validation.constraints.NotNull; import javax.validation.constraints.Size; public class Car { @NotNull private String manufacturer; @NotNull @Size(min = 2, max = 14) private String licensePlate; @Min(2) private int seatCount; public Car(String manufacturer, String licencePlate, int seatCount) { this.manufacturer = manufacturer; this.licensePlate = licencePlate; this.seatCount = seatCount; } }
以上的代码片段,我们应用annotation 来限制
1. `manufacturer`不为 null
2. `licensePlate` string的长度在 2-14之间
3. ·seaCount· 的值最小为2
使用一下代码片段来检验
package tutorial.chapter01;
import java.util.Set;
import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import javax.validation.ValidatorFactory;
import org.junit.BeforeClass;
import org.junit.Test;
import static org.junit.Assert.assertEquals;
public class CarTest {
private static Validator validator;
@BeforeClass
public static void setUp() {
ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
validator = factory.getValidator();
}
@Test
public void manufacturerIsNull() {
Car car = new Car( null, "DD-AB-123", 4 );
Set<ConstraintViolation<Car>> constraintViolations =
validator.validate( car );
//这里我们故意将manufacture 设成 null, 其他项是正确的,我们将返回一个相对应的violation
assertEquals( 1, constraintViolations.size() );
assertEquals( "may not be null", constraintViolations.iterator().next().getMessage() );
}
@Test
public void licensePlateTooShort() {
Car car = new Car( "Morris", "D", 4 );
Set<ConstraintViolation<Car>> constraintViolations =
validator.validate( car );
assertEquals( 1, constraintViolations.size() );
assertEquals(
"size must be between 2 and 14",
constraintViolations.iterator().next().getMessage()
);
}
@Test
public void seatCountTooLow() {
Car car = new Car( "Morris", "DD-AB-123", 1 );
Set<ConstraintViolation<Car>> 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() {
Car car = new Car( "Morris", "DD-AB-123", 2 );
Set<ConstraintViolation<Car>> constraintViolations =
validator.validate( car );
assertEquals( 0, constraintViolations.size() );
}
}
当我们使用 annotation的时候, 编译并执行的时候并不会给我们的限制进行检验,想要检验我们的变量是否满足我们的annotation的限制的时候我们需要使用`ValidatorFactory` 来创建一个 Validator instance. Validator.validate() 方法将会返回 a set of ConstraintViolation. 我们就可以通过观察 这个set来看看我们哪个 变量不符合限制。
Chapter 2.
不同等级的 annotation
a. 变量级别 :从以下代码片段可以看出,我们对class 的变量使用了annotation。这个chapter 1的例子是一样的。
package org.hibernate.validator.referenceguide.chapter02.fieldlevel; public class Car { @NotNull private String manufacturer; @AssertTrue private boolean isRegistered; public Car(String manufacturer, boolean isRegistered) { this.manufacturer = manufacturer; this.isRegistered = isRegistered; } //getters and setters... }
package org.hibernate.validator.referenceguide.chapter02.propertylevel; public class Car { private String manufacturer; private boolean isRegistered; public Car(String manufacturer, boolean isRegistered) { this.manufacturer = manufacturer; this.isRegistered = isRegistered; } @NotNull public String getManufacturer() { return manufacturer; } public void setManufacturer(String manufacturer) { this.manufacturer = manufacturer; } @AssertTrue public boolean isRegistered() { return isRegistered; } public void setRegistered(boolean isRegistered) { this.isRegistered = isRegistered; } }
c. class 级别: 这个是对整个的类的内容进行限制,需要我们自己根据需求进行定制。 以后会提到,先从基础来。
d. 因为不同级别的annotation,我们就会问那夫类和子类之间的继承或者接口是怎么处理的。很好的问题,其实也很简单,那就是无论是继承还是实现我们都会原封不动的接受得到的限制。但是! 接收到的限制不一定会表达,例如以下的例子。 如果我们把 @Valid 注释掉,然后我门对Car 进行 validate, 那么 Person 类是不会被 validate的。要想在validate Car的时候也Validate person那我们需要加上@Valid annotation.
package org.hibernate.validator.referenceguide.chapter02.objectgraph; public class Car { @NotNull //@Valid private Person driver; //... }
package org.hibernate.validator.referenceguide.chapter02.objectgraph; public class Person { @NotNull private String name; //... }
@Valid的作用简单来说就是继续validate 被@Valid 标记的变脸内部的变脸
e.g. 这样的话我们仅仅validate来list是否是 null
@NotNull List<Person> list;
加上valid 才会继续去validate person内部。
@NotNull @Valid List<Person> list;
e. 当得到 constraint violation 之后我门如何通过 ConstraintViolation 的instance来找到我门的violation.
Java Doc - ConstraintViolation 这里是他的方法。我就拿其中一个我觉的有点意思的举个例子. 考虑以下代码,当我们实例化一个valid 的car和person 但是 personname 的age是错的。那当我们得到constraintviolation怎么知道personname的路径在哪里呢? 使用:
gePropertyPath()
结果是
driver.personName.age
Class Car { @NotNull @Valid Person person; //..... } Class Person { @NotNull @Valid PersonName personName; //... } Class PersonName { @Min(18) int age; }
Chapter 03: 方法的parameter 和 return value 的constraint
这章总结来看,主要介绍了如何给一个方法的paramter 和 return value进行constraint validate.