注解验证参数的合法性

package cn.com.songjy.annotation;

public enum ValidateType {

NotNull,Length,Number

}

package cn.com.songjy.annotation;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

@Retention(RetentionPolicy.RUNTIME)
public @interface ValidateAnnotation {

public ValidateType type();

public String errorMsg();

public int length() default 0;

}

package cn.com.songjy.annotation;

import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;

public class ValidateTools {

public static boolean validate(Class obj, HttpServletRequest request){

//Map<String, String> errors = (Map<String, String>) request.getAttribute("errors");
Map<String, String> errors = new HashMap<String, String>();

Field[] fields = obj.getDeclaredFields();

for (Field field : fields) {

//System.out.println(field.getName());//输出所有属性名称

if(field.isAnnotationPresent(ValidateAnnotation.class)){//只处理包含注解为ValidateAnnotation的属性名称

ValidateAnnotation validateUtil = field.getAnnotation(ValidateAnnotation.class);
ValidateType type = validateUtil.type();

if(ValidateType.NotNull == type)
if(true == isNull(field.getName(), request))
errors.put(field.getName(), validateUtil.errorMsg());

if(ValidateType.Length == type)
if(true == length(field.getName(), request, validateUtil.length()))
errors.put(field.getName(), validateUtil.errorMsg());

if(ValidateType.Number == type)
if(true == isNumber(field.getName(), request))
errors.put(field.getName(), validateUtil.errorMsg());
}
}

return errors.size() == 0;
}

public static boolean isNull(String field, HttpServletRequest request){

if(null==request || null==request.getParameter(field)) return true;

if(0==request.getParameter(field).trim().length()) return true;

return false;
}

public static boolean length(String field, HttpServletRequest request, int length){

if(null==request || null==request.getParameter(field)) return true;

if(length>request.getParameter(field).trim().length()) return true;

return false;
}

public static boolean isNumber(String field, HttpServletRequest request){

if(null==request || null==request.getParameter(field)) return true;

try {
Integer.parseInt(request.getParameter(field));
} catch (NumberFormatException e) {
e.printStackTrace();
return true;
}

return false;
}
}

package cn.com.songjy.model;

import cn.com.songjy.annotation.ValidateType;
import cn.com.songjy.annotation.ValidateAnnotation;

public class User {

@ValidateAnnotation(type=ValidateType.Length, errorMsg="用户名长度不能小于1", length=1)
private String username;

@ValidateAnnotation(type=ValidateType.Number, errorMsg="年龄必须是数字")
private int age;

private String[] interest;

public User(){}

public User(String username, int age){
this.username = username;
this.age = age;
}

public String getUsername() {
return username;
}

public void setUsername(String username) {
this.username = username;
}

public int getAge() {
return age;
}

public void setAge(int age) {
this.age = age;
}

public String[] getInterest() {
return interest;
}

public void setInterest(String[] interest) {
this.interest = interest;
}
}

boolean success = ValidateTools.validate(User.class, request);