弹吉他的兔子
1、Java元注解
随意点开一个spring的注解源码，都会看到几个常用的元注解
之前老是看不懂，今天就来弄懂它。
-
注解（Annotation）是一种可以放在 Java 类上，方法上，属性上，参数前面的一种特殊的注释。
-
元注解是用来注释注解的注解，元注解我们平常不会编写，只需要添加到我们自己编写的注解上即可。
Java 自带的常用的元注解有@Target，@Retention，@Documented，@Inherited 分别有如下含义
-
@Target：标记这个注解使用的地方，取值范围是一个枚举 java.lang.annotation.ElementType
-
@Retention：标识这个注解的生命周期，取值范围在枚举 java.lang.annotation.RetentionPolicy
一般定义的注解都是在运行时使用，所有要用
@Retention(RetentionPolicy.RUNTIME) -
@Documented：表示注解是否包含到文档中。 -
@Inherited：使用@Inherited 定义子类是否可继承父类定义的注解Annotation。@Inherited仅针对@Target(ElementType.TYPE)类型的annotation有效，并且仅针对class的继承，对interface的继承无效
2、自定义注解
上面介绍了几个元注解，下面我们定义一个日志注解来演示一下，我们通过定义一个名为OperationLog 的注解来记录一些通用的操作日志，比如记录什么时候什么人查询的哪个表的数据或者新增了什么数据。编写注解我们用的是 @interface 关键字，相关代码如下：
package com.api.annotation;
import java.lang.annotation.*;
/**
* <br>
* <b>Function：</b><br>
* <b>Author：</b>@author 子悠<br>
* <b>Date：</b>2020-11-17 22:10<br>
* <b>Desc：</b>用于记录操作日志<br>
*/
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface OperationLog {
/**
* 操作类型
*
* @return
*/
String type() default OperationType.SELECT;
/**
* 操作说明
*
* @return
*/
String desc() default "";
/**
* 请求路径
*
* @return
*/
String path() default "";
/**
* 是否记录日志，默认是
*
* @return
*/
boolean write() default true;
/**
* 是否需要登录信息
*
* @return
*/
boolean auth() default true;
/**
* 当 type 为 save 时必须
*
* @return
*/
String primaryKey() default "";
/**
* 对应 service 的 Class
*
* @return
*/
Class<?> defaultServiceClass() default Object.class;
}
说明
- 上面的注解，我们增加了
@Target({ElementType.METHOD}),@Retention(RetentionPolicy.RUNTIME),@Documented三个元注解，表示我们这个注解是使用在方法上的，并且生命周期是运行时，而且可以记录到文档中。 - 然后我们可以看到定义注解采用的是
@interface关键字，并且我们给这个注解定义了几个属性，同时设置了默认值。 - 平时我们编写的注解一般必须设置
@Target和@Retention，而且@Retention一般设置为RUNTIME，这是因为我们自定义的注解通常要求在运行期读取，另外一般情况下，不必写@Inherited。
使用
上面的动作只是把注解定义出来了，但是光光定义出来是没有用的，必须有一个地方读取解析，才能提现出注解的价值，我们就采用 Spring 的 AOP 拦截这个注解，将所有携带这个注解的方法所进行的操作都记录下来。
package com.api.config;
import lombok.extern.slf4j.Slf4j;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import javax.servlet.http.HttpServletRequest;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.*;
@Aspect
@Component
@Order(-5)
@Slf4j
public class LogAspect {
/**
* Pointcut for methods which need to record operate log
*/
@Pointcut("within(com.xx.yy.controller..*) && @annotation(com.api.annotation.OperationLog)")
public void logAspect() {
}
/**
* record log for Admin and DSP
*
* @param joinPoint parameter
* @return result
* @throws Throwable
*/
@Around("logAspect()")
public Object around(ProceedingJoinPoint joinPoint) throws Throwable {
Object proceed = null;
String classType = joinPoint.getTarget().getClass().getName();
Class<?> targetCls = Class.forName(classType);
MethodSignature ms = (MethodSignature) joinPoint.getSignature();
Method targetMethod = targetCls.getDeclaredMethod(ms.getName(), ms.getParameterTypes());
OperationLog operation = targetMethod.getAnnotation(OperationLog.class);
if (null != operation && operation.write()) {
SysMenuOpLogEntity opLogEntity = new SysMenuOpLogEntity();
StringBuilder change = new StringBuilder();
if (StrUtil.isNotBlank(operation.type())) {
switch (operation.type()) {
case OperationType.ADD:
proceed = joinPoint.proceed();
String addString = genAddData(targetCls, operation.defaultServiceClass(), joinPoint.getArgs());
opLogEntity.setAfterJson(addString);
change.append(OperationType.ADD);
break;
case OperationType.DELETE:
String deleteString = autoQueryDeletedData(targetCls, operation.primaryKey(), operation.defaultServiceClass(), joinPoint.getArgs());
opLogEntity.setBeforeJson(deleteString);
change.append(OperationType.DELETE);
proceed = joinPoint.proceed();
break;
case OperationType.EDIT:
change.append(OperationType.EDIT);
setOpLogEntity(opLogEntity, targetCls, operation.primaryKey(), operation.defaultServiceClass(), joinPoint.getArgs());
proceed = joinPoint.proceed();
break;
case OperationType.SELECT:
opLogEntity.setBeforeJson(getQueryString(targetCls, operation.defaultServiceClass(), joinPoint.getArgs()));
change.append(operation.type());
proceed = joinPoint.proceed();
break;
case OperationType.SAVE:
savedDataOpLog(opLogEntity, targetCls, operation.primaryKey(), operation.defaultServiceClass(), joinPoint.getArgs());
change.append(operation.type());
proceed = joinPoint.proceed();
break;
case OperationType.EXPORT:
case OperationType.DOWNLOAD:
change.append(operation.type());
proceed = joinPoint.proceed();
break;
default:
}
opLogEntity.setExecType(operation.type());
}
StringBuilder changing = new StringBuilder();
if (StrUtil.isNotBlank(opLogEntity.getExecType())) {
if (operation.auth()) {
LoginUserVO loginUser = getLoginUser();
if (null != loginUser) {
opLogEntity.setUserId(loginUser.getUserId());
opLogEntity.setUserName(loginUser.getUserName());
changing.append(loginUser.getUserName()).append("-");
} else {
log.error("用户未登录");
}
}
opLogEntity.setCreateTime(DateUtils.getCurDate());
opLogEntity.setRemark(getOperateMenuName(targetMethod, operation.desc()));
opLogEntity.setPath(getPath(targetMethod, targetMethod.getName()));
opLogEntity.setChanging(changing.append(change).toString());
menuOpLogService.save(opLogEntity);
}
}
return proceed;
}
/**
* query data by userId
*
* @param targetCls class
* @param defaultServiceClass default service class
* @return
* @throws Exception
*/
private String queryByCurrentUserId(Class<?> targetCls, Class<?> defaultServiceClass) throws Exception {
BaseService baseService = getBaseService(targetCls, defaultServiceClass);
LoginUserVO loginUser = dspBaseService.getLoginUser();
if (null != loginUser) {
Object o = baseService.queryId(loginUser.getUserId());
return JsonUtils.obj2Json(o);
}
return null;
}
/**
* return query parameter
*
* @param targetCls class
* @param args parameter
* @param defaultServiceClass default service class
* @return
* @throws Exception
*/
private String getQueryString(Class<?> targetCls, Class<?> defaultServiceClass, Object[] args) {
if (args.length > 0) {
Class<?> entityClz = getEntityClz(targetCls, defaultServiceClass);
for (Object arg : args) {
if (arg.getClass().equals(entityClz) || arg instanceof BaseModel) {
return JsonUtils.obj2Json(arg);
}
}
}
return null;
}
/**
* save record log while OperatorType is SAVE
*
* @param opLogEntity entity
* @param targetCls class
* @param primaryKey primaryKey
* @param defaultServiceClass default service class
* @param args parameter
* @throws Exception
*/
private void savedDataOpLog(SysMenuOpLogEntity opLogEntity, Class<?> targetCls, String primaryKey, Class<?> defaultServiceClass, Object[] args) throws Exception {
Class<?> entityClz = getEntityClz(targetCls, defaultServiceClass);
BaseService baseService = getBaseService(targetCls, defaultServiceClass);
for (Object arg : args) {
if (arg.getClass().equals(entityClz)) {
if (StrUtil.isNotBlank(primaryKey)) {
Field declaredField = entityClz.getDeclaredField(primaryKey);
declaredField.setAccessible(true);
Object primaryKeyValue = declaredField.get(arg);
//if primary key is not null that means edit, otherwise is add
if (null != primaryKeyValue) {
//query data by primary key
Object o = baseService.queryId(primaryKeyValue);
opLogEntity.setBeforeJson(JsonUtils.obj2Json(o));
}
}
opLogEntity.setAfterJson(JsonUtils.obj2Json(arg));
}
}
}
/**
* set parameter which edit data
*
* @param opLogEntity entity
* @param targetCls class
* @param primaryKey primaryKey
* @param defaultServiceClass default service class
* @param args parameter
* @throws Exception
*/
private void setOpLogEntity(SysMenuOpLogEntity opLogEntity, Class<?> targetCls, String primaryKey, Class<?> defaultServiceClass, Object[] args) throws Exception {
Map<String, String> saveMap = autoQueryEditedData(targetCls, primaryKey, defaultServiceClass, args);
if (null != saveMap) {
if (saveMap.containsKey(ASPECT_LOG_OLD_DATA)) {
opLogEntity.setBeforeJson(saveMap.get(ASPECT_LOG_OLD_DATA));
}
if (saveMap.containsKey(ASPECT_LOG_NEW_DATA)) {
opLogEntity.setBeforeJson(saveMap.get(ASPECT_LOG_NEW_DATA));
}
}
}
/**
* query data for edit and after edit operate
*
* @param targetCls class
* @param primaryKey primaryKey
* @param defaultServiceClass default service class
* @param args parameter
* @return map which data
* @throws Exception
*/
private Map<String, String> autoQueryEditedData(Class<?> targetCls, String primaryKey, Class<?> defaultServiceClass, Object[] args) throws Exception {
if (StrUtil.isBlank(primaryKey)) {
throw new Exception();
}
Map<String, String> map = new HashMap<>(16);
Class<?> entityClz = getEntityClz(targetCls, defaultServiceClass);
BaseService baseService = getBaseService(targetCls, defaultServiceClass);
for (Object arg : args) {
if (arg.getClass().equals(entityClz)) {
Field declaredField = entityClz.getDeclaredField(primaryKey);
declaredField.setAccessible(true);
Object primaryKeyValue = declaredField.get(arg);
//query the data before edit
if (null != primaryKeyValue) {
//query data by primary key
Object o = baseService.queryId(primaryKeyValue);
map.put(ASPECT_LOG_OLD_DATA, JsonUtils.obj2Json(o));
map.put(ASPECT_LOG_NEW_DATA, JsonUtils.obj2Json(arg));
return map;
}
}
}
return null;
}
/**
* return JSON data which add operate
*
* @param targetCls class
* @param args parameter
* @param defaultServiceClass default service class
* @return add data which will be added
* @throws Exception
*/
private String genAddData(Class<?> targetCls, Class<?> defaultServiceClass, Object[] args) throws Exception {
List<Object> parameter = new ArrayList<>();
for (Object arg : args) {
if (arg instanceof HttpServletRequest) {
} else {
parameter.add(arg);
}
}
return JsonUtils.obj2Json(parameter);
}
/**
* query delete data before delete operate
*
* @param targetCls class
* @param primaryKey primaryKey
* @param defaultServiceClass default service class
* @param ids ids
* @return delete data which will be deleted
* @throws Throwable
*/
private String autoQueryDeletedData(Class<?> targetCls, String primaryKey, Class<?> defaultServiceClass, Object[] ids) throws Throwable {
if (StrUtil.isBlank(primaryKey)) {
throw new OriginException(TipEnum.LOG_ASPECT_PRIMARY_KEY_NOT_EXIST);
}
//get service
BaseService baseService = getBaseService(targetCls, defaultServiceClass);
//get entity
Class<?> entityClz = getEntityClz(targetCls, defaultServiceClass);
//query deleted data by primary key
Query query = new Query();
WhereOperator whereOperator = new WhereOperator(entityClz);
Set<Object> set = new HashSet<>(Arrays.asList((Object[]) ids[0]));
whereOperator.and(primaryKey).in(set.toArray());
query.addWhereOperator(whereOperator);
List list = baseService.queryList(query);
return JsonUtils.obj2Json(list);
}
/**
* return service by targetCls
*
* @param targetCls current controller class
* @param defaultServiceClass default service class
* @return service instance
* @throws Exception
*/
private BaseService getBaseService(Class<?> targetCls, Class<?> defaultServiceClass) throws Exception {
//根据类名拿到对应的 service 名称
String serviceName = getServiceName(targetCls, defaultServiceClass);
BaseService baseService;
if (null != defaultServiceClass) {
baseService = (BaseService) ApplicationContextProvider.getBean(serviceName, defaultServiceClass);
} else {
Class<?> type = targetCls.getDeclaredField(serviceName).getType();
baseService = (BaseService) ApplicationContextProvider.getBean(serviceName, type);
}
return baseService;
}
/**
* return service name
*
* @param targetCls current controller class
* @param defaultServiceClass default service class
* @return service name
*/
private String getServiceName(Class<?> targetCls, Class<?> defaultServiceClass) {
if (null != defaultServiceClass && Object.class != defaultServiceClass) {
return StrUtil.left(defaultServiceClass.getSimpleName(), 1).toLowerCase() + defaultServiceClass.getSimpleName().substring(1);
}
return StrUtil.left(targetCls.getSimpleName(), 1).toLowerCase() + targetCls.getSimpleName().substring(1).replace("Controller", "Service");
}
/**
* return entity class
*
* @param targetCls current controller class
* @param defaultServiceClass default service class
* @return entity class
* @throws Exception
*/
private Class<?> getEntityClz(Class<?> targetCls, Class<?> defaultServiceClass) {
try {
Class<?> type;
if (null != defaultServiceClass && Object.class != defaultServiceClass) {
type = defaultServiceClass;
} else {
type = targetCls.getDeclaredField(getServiceName(targetCls, null)).getType();
}
String entityName = type.getName().replace("service", "entity").replace("Service", "Entity");
Class<?> entityClz = Class.forName(entityName);
return entityClz;
} catch (Exception e) {
log.error("获取 class 失败");
}
return null;
}
/**
* require path
*
* @param targetMethod target method
* @param defaultPath default require path
* @return require path
*/
private String getPath(Method targetMethod, String defaultPath) {
String path = defaultPath;
PostMapping postMapping = targetMethod.getAnnotation(PostMapping.class);
GetMapping getMapping = targetMethod.getAnnotation(GetMapping.class);
RequestMapping requestMapping = targetMethod.getAnnotation(RequestMapping.class);
if (null != postMapping) {
path = postMapping.value()[0];
} else if (null != getMapping) {
path = getMapping.value()[0];
} else if (null != requestMapping) {
path = requestMapping.value()[0];
}
return path;
}
}
上面的代码中我们定义了一个切面指定需要拦截的包名和注解，因为涉及到很多业务相关的代码，所以不能完整的提供出来，但是整个思路就是这样的，在每种操作类型前后将需要记录的数据查询出来进行记录。代码很长主要是用来获取相应的参数值的，大家使用的时候可以根据自己的需要进行取舍。比如在新增操作的时候，我们将新增的数据进行记录下来；编辑的时候将编辑前的数据查询出来和编辑后的数据一起保存起来，删除也是一样的，在删除前将数据查询出来保存到日志表中。
同样导出和下载都会记录相应信息，整个操作类型的代码如下：
package com.api.annotation;
/**
* <br>
* <b>Function：</b><br>
* <b>Author：</b>@author 子悠<br>
* <b>Date：</b>2020-11-17 22:11<br>
* <b>Desc：</b>无<br>
*/
public interface OperationType {
/**
* 新增
**/
String ADD = "add";
/**
* 删除
**/
String DELETE = "delete";
/**
* 使用实体参数修改
**/
String EDIT = "edit";
/**
* 查询
**/
String SELECT = "select";
/**
* 新增和修改的保存方法，使用此类型时必须配置主键字段名称
**/
String SAVE = "save";
/**
* 导出
**/
String EXPORT = "export";
/**
* 下载
**/
String DOWNLOAD = "download";
}
后续在使用的时候只需要在需要的方法上加上注解，填上相应的参数即可@OperationLog(desc = "查询单条记录", path = "/data")