@在没有控制器的情况下使用jackson创建对象时有效

  • Z时代
  • 2024-01-10
  • 分类：问答

我有一个模型，当从前端发送请求时，我可以在控制器中使用@Valid进行验证：

@NotNull
@Size(min=1, message="Name should be at least 1 character.")
private String name;
@NotNull
@Pattern(regexp = "^https://github.com/.+/.+$", message = "Link to github should match https://github.com/USER/REPOSITORY")
private String github;

但是现在，我还使用不含控制器的Jackson的ObjectMapper创建了一个对象。有没有一种方法可以在ObjectMapper中注册此验证，还是应该只检查setter中的变量？

回答：

BeanDeserializer反序列化后，您可以扩展和验证对象。要注册此bean使用SimpleModule。

具有验证的简单bean反序列化器：

class BeanValidationDeserializer extends BeanDeserializer {
    private final static ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
    private final Validator validator = factory.getValidator();
    public BeanValidationDeserializer(BeanDeserializerBase src) {
        super(src);
    }
    @Override
    public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
        Object instance = super.deserialize(p, ctxt);
        validate(instance);
        return instance;
    }
    private void validate(Object instance) {
        Set<ConstraintViolation<Object>> violations = validator.validate(instance);
        if (violations.size() > 0) {
            StringBuilder msg = new StringBuilder();
            msg.append("JSON object is not valid. Reasons (").append(violations.size()).append("): ");
            for (ConstraintViolation<Object> violation : violations) {
                msg.append(violation.getMessage()).append(", ");
            }
            throw new ConstraintViolationException(msg.toString(), violations);
        }
    }
}

我们可以如下使用它：

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.BeanDescription;
import com.fasterxml.jackson.databind.DeserializationConfig;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.deser.BeanDeserializer;
import com.fasterxml.jackson.databind.deser.BeanDeserializerBase;
import com.fasterxml.jackson.databind.deser.BeanDeserializerModifier;
import com.fasterxml.jackson.databind.module.SimpleModule;
import javax.validation.ConstraintViolation;
import javax.validation.ConstraintViolationException;
import javax.validation.Validation;
import javax.validation.Validator;
import javax.validation.ValidatorFactory;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Pattern;
import javax.validation.constraints.Size;
import java.io.File;
import java.io.IOException;
import java.util.Set;
public class JsonApp {
    public static void main(String[] args) throws Exception {
        File jsonFile = new File("./resource/test.json").getAbsoluteFile();
        SimpleModule validationModule = new SimpleModule();
        validationModule.setDeserializerModifier(new BeanDeserializerModifier() {
            @Override
            public JsonDeserializer<?> modifyDeserializer(DeserializationConfig config, BeanDescription beanDesc, JsonDeserializer<?> deserializer) {
                if (deserializer instanceof BeanDeserializer) {
                    return new BeanValidationDeserializer((BeanDeserializer) deserializer);
                }
                return deserializer;
            }
        });
        ObjectMapper mapper = new ObjectMapper();
        mapper.registerModule(validationModule);
        System.out.println(mapper.readValue(jsonFile, Pojo.class));
    }
}
class Pojo {
    @NotNull
    @Size(min = 1, message = "Name should be at least 1 character.")
    private String name;
    @NotNull
    @Pattern(regexp = "^https://github.com/.+/.+$", message = "Link to github should match https://github.com/USER/REPOSITORY")
    private String github;
    // getters, setters, toString()
}

For valid JSON payload:

{
  "name": "Jackson",
  "github": "https://github.com/FasterXML/jackson-databind"
}

prints:

Pojo{name='Jackson', github='https://github.com/FasterXML/jackson-databind'}

For invalid JSON payload:

{
  "name": "",
  "github": "https://git-hub.com/FasterXML/jackson-databind"
}

prints:

Exception in thread "main" javax.validation.ConstraintViolationException: JSON object is not valid. Reasons (2): Name should be at least 1 character., Link to github should match https://github.com/USER/REPOSITORY, 
    at BeanValidationDeserializer.validate(JsonApp.java:110)
    at BeanValidationDeserializer.deserialize(JsonApp.java:97)

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