Bean Validation

CustomConstraint.java

package sample;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import javax.validation.Constraint;

@Target({ ElementType.METHOD, ElementType.FIELD, ElementType.PARAMETER })
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = sample.CustomValidator.class)
public @interface CustomConstraint {

    String message() default "message.custom.invalid";
    Class[] groups() default {};
    Class[] payload() default {};
}

CustomValidator.java

package sample;

import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;

public class CustomValidator implements ConstraintValidator<CustomConstraint, Object> {

    private Validator[] validators;

    @Override
    public void initialize(CustomConstraint constraintAnnotation) {
        this.validators = getInstancesOf(constraintAnnotation.payload());
    }

    @Override
    public boolean isValid(Object value, ConstraintValidatorContext context) {
        context.disableDefaultConstraintViolation();

        boolean valid = true;
        for (Validator validator : this.validators) {
            Message[] errors = validator.validate(value); // ①
            if (errors != null && errors.length > 0) {
                for (Message error : errors) {
                    context.buildConstraintViolationWithTemplate(error.getMsg()).addConstraintViolation();
                    valid = false;
                }
            }
        }
        return valid;
    }

    public static <T> Validator[] getInstancesOf(Class[] classes) {
        … // classからValdatorのインスタンスを生成する 
    }
}

Document.java

package sample;

import javax.validation.constraints.NotNull;
import javax.validation.Valid;
import sample.CustomConstraint;
import sample.Validators.Id;

public class Document {

    @CustomConstraint(payload = Id.class) // ③
    private Long id;

    @NotNull // ④
    private String text;

    @Valid // ⑤
    private Edtior editor;
    ...
}

DocumentController.java

package sample;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.validation.Valid;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;
import sample.CustomConstraint;
import sample.Validators.DocumentSaveMode;

@Controller
public class DocumentController {
    @RequestMapping(value = "document",
            method = RequestMethod.PUT,
            consumes = "application/json",
            produces = "application/json")
        @ResponseBody public Document saveDocument(
                final HttpServletRequest request,
                final HttpServletResponse response,
                final @RequestBody @Valid Document doc, // ①
                final BindingResult result // ②
        ) {
...
    }

Message.java

package sample;

public class Message {
    private final String msg;
    private final Object[] params;
    ...
}

Validator.java

package sample;

public interface Validator<T> {
    Message[] validate(T value);
}

Validators.java

package sample;

import javax.validation.Payload;
import sample.Message;
import sample.Validator;
import sample.DocumentSaveMode;

public final class Validators {
    public static class Id implements Payload, Validator<Long> {

        @Override
        public Message[] validate(Long value) {
            return ...; // 値をバリデーションしてエラーがあればMessageを返す。
        }
        ...
    }

    public static class DocumentSaveMode implements Payload, Validator<DocumentSaveMode> {

        @Override
        public Message[] validate(DocumentSaveMode value) {
            return ...; // 値をバリデーションしてエラーがあればMessageを返す。
        }
        ...
    }
    ...
}

WebConfig.java

package sample;

import org.springframework.context.MessageSource;
import org.springframework.context.annotation.Bean;
import org.springframework.context.support.ResourceBundleMessageSource;
import org.springframework.validation.Validator;
import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

@EnableWebMvc
public abstract class WebConfig extends WebMvcConfigurerAdapter {

    private final MessageSource messageSource;
    {
        ResourceBundleMessageSource bean = new ResourceBundleMessageSource();
        bean.setBasenames("message");
        bean.setDefaultEncoding("utf-8");
        this.messageSource = bean;
    }

    @Bean
    public MessageSource messageSource() {
        return this.messageSource;
    }

    @Bean
    public LocalValidatorFactoryBean validator() {
        LocalValidatorFactoryBean bean = new LocalValidatorFactoryBean();
        bean.setValidationMessageSource(this.messageSource);
        return bean;
    }

    @Override
    public Validator getValidator() {
        return validator();
    }
    
    ...
}