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022.自定义注解
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注解是Jdk1.5新增新技术。很多框架为了简化代码，都会提供有些注解。 可以理解为插件，是代码级别的插件，在类的方法上写：@XXX，就是在代码上插入了一个插件。 注解不会也不能影响代码的实际逻辑，仅仅起到辅助性的作用。
定义
Java文件中叫做Annotation，用@interface表示。
元注解
@interface上面按需要注解上一些东西， 包括 @Retention、@Target、@Document、@Inherited四种。
注解的保留策略
// 注解仅存在于源码中，在class字节码文件中不包含 @Retention(RetentionPolicy.SOURCE) // 默认的保留策略，注解会在class字节码文件中存在，但运行时无法获得 @Retention(RetentionPolicy.CLASS) // 注解会在class字节码文件中存在，在运行时可以通过反射获取到 @Retention(RetentionPolicy.RUNTIME)
注解的作用目标
// 接口、类、枚举、注解 @Target(ElementType.TYPE) // 字段、枚举的常量 @Target(ElementType.FIELD) // 方法 @Target(ElementType.METHOD) // 方法参数 @Target(ElementType.PARAMETER) // 构造函数 @Target(ElementType.CONSTRUCTOR) // 局部变量 @Target(ElementType.LOCAL_VARIABLE) // 注解 @Target(ElementType.ANNOTATION_TYPE) // 包 @Target(ElementType.PACKAGE)
注解包含在javadoc中
@Documented
注解可以被继承
@Inherited
通过注解进行校验
demo1
package cn.qbz.thread.day1121;
import java.lang.annotation.*;
@Documented
@Inherited
@Target({ElementType.FIELD, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface UserAnnotation {
int min() default 0;
int max() default 120;
boolean isNotNull() default true;
}package cn.qbz.thread.day1121;
public class User {
@UserAnnotation(isNotNull = true)
private String name;
@UserAnnotation(min = 18, max = 50)
private Integer age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
}package cn.qbz.thread.day1121;
import java.lang.reflect.Field;
public class UserCheck {
public static boolean check(User user) throws Exception {
if (user == null) {
System.out.println("user is null.");
return false;
}
Field[] fields = User.class.getDeclaredFields();
for (Field field : fields) {
field.setAccessible(true);
UserAnnotation userAnnotation = field.getAnnotation(UserAnnotation.class);
String name = field.getName();
Object value = field.get(user);
int min = userAnnotation.min();
int max = userAnnotation.max();
boolean isNull = userAnnotation.isNotNull();
if (isNull) {
if (value == null) {
throw new Exception(name + " is null.");
}
int length = value.toString().length();
if (length < min) {
throw new Exception(name + " length min is " + min);
}
if (length > max) {
throw new Exception(name + " length max is " + max);
}
}
}
return true;
}
}package cn.qbz.thread.day1121;
public class AnnotationTest {
public static void main(String[] args) throws Exception {
User user = new User();
user.setAge(3);
user.setName("sdfaf");
UserCheck.check(user);
}
}demo2
<dependency>
<groupId>javax.validation</groupId>
<artifactId>validation-api</artifactId>
<version>1.1.0.Final</version>
</dependency>package com.antzb.chaos.annotations;
import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import com.antzb.chaos.constant.ConstantKey;
import com.antzb.chaos.utils.CommonUtil;
import org.springframework.util.StringUtils;
import javax.validation.Constraint;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
import javax.validation.Payload;
import java.lang.annotation.*;
import java.util.ArrayList;
import java.util.List;
/**
* @Author: qubianzhong
* @Date: 18-4-12 下午1:38
*/
@Documented
@Target({ElementType.PARAMETER, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Constraint(validatedBy = ProjectUpdateTemplate.OrderByValidator.class)
public @interface ProjectUpdateTemplate {
String message() default "[任务步骤格式有误！]";
Class<?>[] groups() default {};
Class<? extends Payload>[] payload() default {};
class OrderByValidator implements ConstraintValidator<ProjectUpdateTemplate, JSONObject> {
@Override
public void initialize(ProjectUpdateTemplate projectUpdateTemplate) {
}
@Override
public boolean isValid(JSONObject template, ConstraintValidatorContext context) {
context.disableDefaultConstraintViolation();
boolean isRight = true;
String errorMessage = "";
if (template != null && template.size() > 0) {
for (String key : template.keySet()) {
JSONObject element = template.getJSONObject(key);
if (element == null) {
isRight = false;
errorMessage = "任务步骤序号异常！必须为:1,2,3,4的字符串.";
break;
}
}
} else {
isRight = false;
errorMessage = "任务步骤不能为空";
}
context.buildConstraintViolationWithTemplate(errorMessage).addConstraintViolation();
return isRight;
}
}
}public class ProjectUpdateTemplateReq {
@NotNull
private Integer projectInfoId;
@ProjectUpdateTemplate
private JSONObject stepTemplate;
public Integer getProjectInfoId() {
return projectInfoId;
}
public void setProjectInfoId(Integer projectInfoId) {
this.projectInfoId = projectInfoId;
}
public JSONObject getStepTemplate() {
return stepTemplate;
}
public void setStepTemplate(JSONObject stepTemplate) {
this.stepTemplate = stepTemplate;
}
} @PostMapping
public ResultMessage updateProjectOfTemplate(@Valid @RequestBody ProjectUpdateTemplateReq projectUpdateTemplateReq) {
}demo3
package com.rongyi.smart.web.checker.annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface CheckLogin {
}package com.antzb.chaos.www.aspect;
import com.antzb.chaos.annotations.CheckLogin;
import com.antzb.chaos.constant.ConstantKey;
import com.antzb.chaos.www.util.JwtTokenUtil;
import io.jsonwebtoken.Claims;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.stereotype.Component;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import javax.servlet.http.HttpServletRequest;
import java.sql.Timestamp;
/**
* @Author: qubianzhong
* @Date: 18-5-4 上午10:01
*/
@Component
@Aspect
public class CheckLoginAspect {
@Pointcut("@annotation(checkLogin)")
public void checkLoginPointCut(CheckLogin checkLogin) {
}
@Before("checkLoginPointCut(checkLogin)")
public void doBefore(JoinPoint joinPoint, CheckLogin checkLogin) {
String message = "请扫码登录后重新访问!";
ServletRequestAttributes sra = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
HttpServletRequest request = sra.getRequest();
request.setAttribute(ConstantKey.HTTPSERVLETREQUEST_ATTRIBUTES_CHECKLOGIN, true);
String token = request.getHeader(ConstantKey.JWT_HEADER_KEY);
if (token == null) {
throw new SecurityException(message);
}
Claims claims = JwtTokenUtil.getClaimsFromToken(token.replace(ConstantKey.JWT_TOKENHEAD_KEY, ""));
if (claims == null) {
throw new SecurityException(message);
}
Object userName = claims.get(JwtTokenUtil.CLAIM_KEY_USERNAME);
Object userId = claims.get(JwtTokenUtil.CLAIM_KEY_USERID);
Timestamp expirationTime = new Timestamp(claims.getExpiration().getTime());
if (userId == null
|| userName == null
|| expirationTime == null
|| expirationTime.before(new Timestamp(System.currentTimeMillis()))) {
throw new SecurityException(message);
}
}
@After("checkLoginPointCut(checkLogin)")
public void doAfter(CheckLogin checkLogin) {
}
} @GetMapping("/task/list")
@CheckLogin
public ResultMessage queryProjectTaskList() {
ResultMessage resultMessage = new ResultMessage();
//......
return resultMessage;
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