[Spring] Spring Assert Statements

Spring Assert Statements

package org.springframework.util;

인수를 검증하고 예외를 발생시키는 유용한 클래스

Assert Class

Spring Assert 특징

• Assert 메서드는 정적
• 예상되는 인수를 가정하고, 조건이 충족되지 않으면 런타임 예외를 발생
• 첫 번째 매개 변수는 검증을 위한 인수 또는 확인할 논리적 조건
• 두 번째 매개 변수는 유효성 검사에 실패할 경우 표시되는 예외 메시지

Example

public class Car {
    private String state = "stop";

    /**
     * speed > 0 조건을 충족하지 않을 경우 런타임 예외 발생
     */
    public void drive(int speed) {
        Assert.isTrue(speed > 0, "speed must be positive");
        this.state = "drive";
        // ...
    }
}

Assert.isTrue(speed > 0, "speed must be positive"); 코드를 풀어쓴다면 아래와 같이 작성할 수 있다.

if (!(speed > 0)) {
    throw new IllegalArgumentException("speed must be positive");
}

Assertions

Class Assert

Logical Assertions

isTrue

• Assert a boolean expression, throwing an IllegalArgumentException if the expression evaluates to false.

state

• Assert a boolean expression, throwing an IllegalStateException if the expression evaluates to false.

  public void fuel() {
      Assert.state(this.state.equals("stop"), "car must be stopped");
      // ...
  }

Object and Type Assertions

notNull

• Assert that an object is not null.

  public void сhangeOil(String oil) {
    Assert.notNull(oil, "oil mustn't be null");
    // ...
  }

isNull

• Assert that an object is null.

  public void replaceBattery(CarBattery carBattery) {
      Assert.isNull(
        carBattery.getCharge(), 
        "to replace battery the charge must be null");
      // ...
  }

isInstanceOf

• Assert that the provided object is an instance of the provided class.

  public void сhangeEngine(Engine engine) {
      Assert.isInstanceOf(ToyotaEngine.class, engine);
      // ...
  }

isAssignable

• Assert that superType.isAssignableFrom(subType) is true.

  public void repairEngine(Engine engine) {
      Assert.isAssignable(Engine.class, ToyotaEngine.class);
      // ...
  }

Text Assertions

hasLength

• Assert that the given String is not empty; that is, it must not be null and not the empty String.

  public void startWithHasLength(String key) {
      Assert.hasLength(key, "key must not be null and must not the empty");
      // ...
  }

hasText

• Assert that the given String contains valid text content; that is, it must not be null and must contain at least one non-whitespace character.

  public void startWithHasText(String key) {
      Assert.hasText(
        key, 
        "key must not be null and must contain at least one non-whitespace  character");
      // ...
  }

doesNotContain

• Assert that the given text does not contain the given substring.

  public void startWithNotContain(String key) {
      Assert.doesNotContain(key, "123", "key mustn't contain 123");
      // ...
  }

Collection and Map Assertions

notEmpty() for Collections

• Assert that a collection contains elements; that is, it must not be null and must contain at least one element.

  public void repair(Collection<String> repairParts) {
      Assert.notEmpty(
        repairParts, 
        "collection of repairParts mustn't be empty");
      // ...
  }

notEmpty() for Maps

• Assert that a Map contains entries; that is, it must not be null and must contain at least one entry.

  public void repair(Map<String, String> repairParts) {
      Assert.notEmpty(
        repairParts, 
        "map of repairParts mustn't be empty");
      // ...
  }

Array Assertions

notEmpty() for Arrays

• Assert that an array contains elements; that is, it must not be null and must contain at least one element.

  public void repair(String[] repairParts) {
      Assert.notEmpty(
        repairParts, 
        "array of repairParts mustn't be empty");
      // ...
  }

noNullElements

• Assert that an array contains no null elements.

  public void repairWithNoNull(String[] repairParts) {
      Assert.noNullElements(
        repairParts, 
        "array of repairParts mustn't contain null elements");
      // ...
  }

Reference

Spring Assert Statements

Class Assert