java反射和自定义注解的综合应用

前言

前几天学习了反射和自定义注解，刚好工作中遇到一个小问题：前台传递到后台的必填字段为空，导致不能插入数据库。就是这样一个小问题，让我考虑到是否可以做一个通用的方法，让前台传递过来的必填字段在后台也校验一遍，如果传递为空，则把响应字段返回提示。因此，我考虑的是用注解的方式，在必填字段上面定义，利用反射得到必填字段的字段名，判断是否为空，并返回响应的信息。

需求模拟

假设客户有：姓名，年龄，地址，手机号码，身份证号等信息，而我们是做金融业务，所以关键是看客户的三要素：姓名，身份证号，手机号码。我们要保证前台传递过来的这三个值不为空。

废话不多说，直接上代码。只看红框里面的即可。

目录结构

客户信息类：Customer

这个是个实体类，我们在：姓名，身份证号码，手机号码上都用了我们的自定义注解。

package com.dao.chu.po;/** * * <p>Title: Customer</p>* <p>Description:客户信息实体 </p> */public class Customer {private int id;@IsRequiredprivate String name; // 姓名@IsRequiredprivate String idnum; // 身份证号码@IsRequiredprivate String phone; // 手机号private String sex; // 性别private int age; // 年龄private String address; // 地址@Overridepublic String toString() {return "Customer [id=" + id + ", name=" + name + ", idnum=" + idnum+ ", phone=" + phone + ", sex=" + sex + ", age=" + age+ ", address=" + address + "]";}public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getIdnum() {return idnum;}public void setIdnum(String idnum) {this.idnum = idnum;}public String getPhone() {return phone;}public void setPhone(String phone) {this.phone = phone;}public String getSex() {return sex;}public void setSex(String sex) {this.sex = sex;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}}

自定义注解类：IsRequired

package com.dao.chu.po;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;/** * * <p>Title: IsRequired</p>* <p>Description: 字段是否必填 </p> */@Retention(value = RetentionPolicy.RUNTIME)  @Target(value = {ElementType.FIELD})  public @interface IsRequired  {      /**     *          * <p>Title: isRequired</p>    * <p>Description:true:必填  false:非必填 </p>    * @return     */    boolean isRequired() default true;  }  

关键工具类：PoUtils

我们在这个类里面主要用了反射的知识，得到带有自定义注解的字段，并取得这个对象的值进行判断

package com.dao.chu.po;    import java.beans.IntrospectionException;import java.beans.PropertyDescriptor;import java.lang.reflect.Field;import java.lang.reflect.InvocationTargetException;import javax.jws.WebResult;import com.sun.xml.internal.ws.util.StringUtils;  /** * * <p>Title: PoUtils</p>* <p>Description:Po操作工具类  </p> */@SuppressWarnings("unused")  public class PoUtils  {        /*** <p>Title: getProperties</p>* <p>Description: 获取javabean属性通用方法 </p>* @param t* @param beanName* @return* @throws IllegalAccessException* @throws IllegalArgumentException* @throws InvocationTargetException* @throws IntrospectionException */    private static <T> Object getProperties(T t, String beanName)          throws IllegalAccessException, IllegalArgumentException, InvocationTargetException, IntrospectionException      {          Object nameValue = new PropertyDescriptor(beanName, t.getClass()).getReadMethod().invoke(t);          return nameValue;      }            /**    * <p>Title: IsFieldBlank</p>    * <p>Description:判断前台传过来的必填字段是否为空 ,不正确则将相应字段返回  </p>    * @param t    * @return    * @throws IllegalAccessException    * @throws IllegalArgumentException    * @throws InvocationTargetException    * @throws IntrospectionException     */    public static <T> RespBody IsFieldBlank(T t)          throws IllegalAccessException, IllegalArgumentException, InvocationTargetException, IntrospectionException      {      RespBody respBody = new RespBody();        StringBuffer sb = new StringBuffer();                    Field[] declaredFields = t.getClass().getDeclaredFields();          for (Field field : declaredFields)          {              field.setAccessible(true);              String name = field.getName();              boolean fieldHasAnno = field.isAnnotationPresent(IsRequired.class);              if (fieldHasAnno)              {                  IsRequired annotation = field.getAnnotation(IsRequired.class);                  boolean required = annotation.isRequired();                  if (required)                  {                      Object value = getProperties(t, name);                      if (null == value)                      {                          sb.append(name + ",");                      }                  }              }          }                    if (null==sb.toString()||"".equals(sb.toString()))          {          respBody.isSuccess();        }                    respBody.setSuccess(false);        respBody.setMsg(sb.toString().substring(0,sb.toString().lastIndexOf(",")) + " is required");          return respBody;      }  }  

RespBody：响应实体类

封装了响应的成功失败以及一些信息

package com.dao.chu.po;/** * * <p>Title: RespBody</p>* <p>Description: 响应实体类</p> */public class RespBody  {      private boolean isSuccess = true;            private String msg;            private Object data;            public boolean isSuccess()      {          return isSuccess;      }            public void setSuccess(boolean isSuccess)      {          this.isSuccess = isSuccess;      }            public String getMsg()      {          return msg;      }            public void setMsg(String msg)      {          this.msg = msg;      }            public Object getData()      {          return data;      }            public void setData(Object data)      {          this.data = data;      }            public RespBody(boolean isSuccess, String msg, Object data)      {          super();          this.isSuccess = isSuccess;          this.msg = msg;          this.data = data;      }            public RespBody(boolean isSuccess, String msg)      {          super();          this.isSuccess = isSuccess;          this.msg = msg;      }            public RespBody()      {      }            @Override      public String toString()      {          return "ReturnBody [isSuccess=" + isSuccess + ", msg=" + msg + ", data=" + data + "]";      }  }  

测试类：IsRequiredTest

package com.dao.chu.po;/** * * <p>Title: IsRequiredTest</p>* <p>Description: 必填成员变量测试类</p> */public class IsRequiredTest {public static void main(String[] args) {Customer customer = new Customer();try {//=========第一次不赋值==========RespBody respBody = PoUtils.IsFieldBlank(customer);//不通过则返回提示信息if (!respBody.isSuccess()) {System.out.println("1."+respBody.getMsg());}//=========第二次给姓名赋值==========customer.setName("张三");respBody = PoUtils.IsFieldBlank(customer);//不通过则返回提示信息if (!respBody.isSuccess()) {System.out.println("2."+respBody.getMsg());}} catch (Exception e) {e.printStackTrace();}}}

输出结果

第一次三个值都为空，提示三个都是必填的，第二次因为姓名赋值了，所以提示另外两个是必填的，本次实验宣告结束，本人知识有限，若有更好的方法欢迎指正