Java自定义注解源码+原理解释(使用Java自定义注解校验bean传入参数合法性)java

前言：因为前段时间忙于写接口，在接口中须要作不少的参数校验，本着简洁、高效的原则，便写了这个小工具供本身使用(内容为缩减版，具体业务可自行扩展)app

思路：使用Java反射机制，读取实体类属性头部注解，经过get方法获取参数值进行校验，若是为空则进行异常抛出。ide

CheckNull.java 类工具

package com.seesun2012.common.annotation;

import java.lang.annotation.Documented;

import java.lang.annotation.ElementType;

import java.lang.annotation.Inherited;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

import java.lang.annotation.Target;

/**

* 自定义注解：校验非空字段

*

* @author seesun2012@163.com

*

*/

@Documented

@Inherited

// 接口、类、枚举、注解

@Target(ElementType.FIELD)

//只是在运行时经过反射机制来获取注解，而后本身写相应逻辑(所谓注解解析器)

@Retention(RetentionPolicy.RUNTIME)

public @interface CheckNull {

String message();

}

Userregister.java 类ui

package com.seesun2012.common.entity;

import java.io.Serializable;

import com.seesun2012.common.annotation.CheckNull;

/**

* 用户注册实体类

*

* @author seesun2012@163.com

*

*/

public class Userregister implements Serializable{

private static final long serialVersionUID = 1L;

//自定义注解

@CheckNull(message="用户名不能为空")

private String userAccount;

//自定义注解

@CheckNull(message="密码不能为空")

private String passWord;

public String getUserAccount() { return userAccount; }

public void setUserAccount(String userAccount) { this.userAccount = userAccount; }

public String getPassWord() { return passWord; }

public void setPassWord(String passWord) { this.passWord = passWord; }

@Override

public String toString() {

StringBuilder sb = new StringBuilder();

sb.append(getClass().getSimpleName());

sb.append(" [");

sb.append("Hash = ").append(hashCode());

sb.append(", userAccount=").append(userAccount);

sb.append(", passWord=").append(passWord);

sb.append(", serialVersionUID=").append(serialVersionUID);

sb.append("]");

return sb.toString();

}

}

CommonUtils.java 类this

package com.seesun2012.common.utils;

import java.beans.BeanInfo;

import java.beans.Introspector;

import java.beans.PropertyDescriptor;

import java.lang.reflect.Field;

import java.lang.reflect.Method;

import java.util.List;

import com.seesun2012.common.annotation.CheckNull;

import com.seesun2012.common.exception.CustBusinessException;

/**

* 公共工具类

*

* @author seesun2012@163.com

*

*/

public class CommonUtils{

/**

* 经过反射来获取javaBean上的注解信息，判断属性值信息，而后经过注解元数据来返回

*/

public static boolean doValidator(T clas){

Class> clazz = clas.getClass();

Field[] fields = clazz.getDeclaredFields();

for (Field field : fields) {

CheckNull checkNull = field.getDeclaredAnnotation(CheckNull.class);

if (null!=checkNull) {

Object value = getValue(clas, field.getName());

if (!notNull(value)) {

throwExcpetion(checkNull.message());

}

}

}

return true;

}

/**

* 获取当前fieldName对应的值

*

* @param clas对应的bean对象

* @param fieldNamebean中对应的属性名称

* @return

*/

public static Object getValue(T clas,String fieldName){

Object value = null;

try {

BeanInfo beanInfo = Introspector.getBeanInfo(clas.getClass());

PropertyDescriptor[] props = beanInfo.getPropertyDescriptors();

for (PropertyDescriptor property : props) {

if (fieldName.equals(property.getName())) {

Method method = property.getReadMethod();

value = method.invoke(clas, new Object[]{});

}

}

} catch (Exception e) {

e.printStackTrace();

}

return value;

}

/**

* 非空校验

*

* @param value

* @return

*/

public static boolean notNull(Object value){

if(null==value){

return false;

}

if(value instanceof String && isEmpty((String)value)){

return false;

}

if(value instanceof List && isEmpty((List>)value)){

return false;

}

return null!=value;

}

public static boolean isEmpty(String str){

return null==str || str.isEmpty();

}

public static boolean isEmpty(List> list){

return null==list || list.isEmpty();

}

private static void throwExcpetion(String msg) {

if(null!=msg){

throw new CustBusinessException(msg);

}

}

}

Result.java 类code

package com.seesun2012.common.entity;

import java.io.Serializable;

import java.util.HashMap;

public class Result extends HashMap implements Serializable {

private static final long serialVersionUID = 1L;

public static final Result SUCCEED = new Result(0, "操做成功");

public Result(int status, String massage) {

super();

this.put("status", status).put("message", massage);

}

public Result put(String key, Object value) {

super.put(key, value);

return this;

}

public static Result build(int i, String message) {

return new Result(i, message);

}

}

CustBusinessException.java 类对象

package com.seesun2012.common.exception;

/**

* 自定义异常类

*

* @author seesun2012@163.com

*

*/

public class CustBusinessException extends RuntimeException{

private static final long serialVersionUID = 1L;

public CustBusinessException(){

}

public CustBusinessException(String str){

super(str);

}

public CustBusinessException(Throwable throwable){

super(throwable);

}

public CustBusinessException(String str, Throwable throwable){

super(str, throwable);

}

}

TestUtils.java 类接口

package com.seesun2012.test.utils;

import com.seesun2012.common.entity.Result;

import com.seesun2012.common.entity.Userregister;

import com.seesun2012.common.utils.CommonUtils;

public class TestUtils{

public static void main(String[] args) {

Userregister sss = new Userregister();

sss.setUserAccount("asdflkjasokdfj");

System.out.println(insertUser(sss));

}

public static Result insertUser(Userregister param){

Result result = new Result(1, "新增失败");

try {

CommonUtils.doValidator(param);

result = Result.build(0, "新增成功");

} catch (Exception e) {

result = Result.build(1, e.getMessage());

}

return result;

}

}

结语：该用户暂未添加ip