问题描述
我在配置文件中有一些值，应该是JSON(将作为字符串加载).
I have some value from my configuration file, that should be a JSON (which will be loaded as a String).
我希望Spring在注入它并抛出其他错误之前先验证该值确实是有效的JSON.
I'd like Spring to validate that this value is indeed a valid JSON before injecting it and throw an error else.
我已经阅读了有关存在的验证注释，例如-@NotNull, @Size, @Min, @Max, @Email, @NotEmpty等.
I've read about the validation annotations that exist, such as - @NotNull, @Size, @Min, @Max, @Email, @NotEmpty etc.
有什么方法可以创建自定义验证器?
Is there any way to create a custom validator?
我想要一个验证器，它将尝试将String转换为JSON，如以下示例所示:
I want a validator that will attempt to convert the String to JSON, as in the following example:
如何在Java中将jsonString转换为JSONObject .
推荐答案
可用的验证批注未提供此功能，因此您必须进行自定义实现.该任务分为2个简单步骤:
This is not provided by available validation annotations, therefore you have to go for a custom implementation. The task is divided into 2 simple steps:
1.给定的String是否为JSON格式
有多个库可以解析(因此验证)一个String是否遵循JSON语法标准.让我们以我最喜欢的GSON为例(有).这取决于您当前使用的是哪个库:
There are multiple libraries that are able to parse (therefore validate) a String whether follows the JSON syntax standard. Let's use my favourite GSON for example (there are many). It depends on what library do you currently use:
String string = "{\"foo\":\"bar\"}"
JsonParser jsonParser = new JsonParser();
try {
jsonParser.parse(string); // valid JSON
} catch (JsonSyntaxException ex) {
/* exception handling */ // invalid JSON
}
2.自定义验证批注
首先提供一个启用验证的依赖项:
Start with providing a dependency enabling validations:
- groupId:
org.hibernate - artifactId:
hibernate-validator
- groupId:
org.hibernate - artifactId:
hibernate-validator
创建用于验证的注释:
@Documented
@Constraint(validatedBy = ContactNumberValidator.class)
@Target( { ElementType.METHOD, ElementType.FIELD })
@Retention(RetentionPolicy.RUNTIME)
public @interface JsonString {
String message() default "The String is not in JSON format";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
}
...以及验证器通过注释处理验证:
... and the validator handling the validation through the annotation:
public class JsonStringValidator implements ConstraintValidator<JsonString, String> {
@Override
public void initialize(JsonString jsonString) { }
@Override
public boolean isValid(String string, ConstraintValidatorContext context) {
// Use an implementation from step 1. A brief example:
try {
new JsonParser().parse(string);
return true; // valid JSON, return true
} catch (JsonSyntaxException ex) {
/* exception handling if needed */
}
return false; // invalid JSON, return false
}
}
用法非常简单:
@JsonString
private String expectedJsonString
在 Baeldung的中详细描述了此实现.
This implementation is described in detail at Baeldung's.
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