如何在SpringBootMongoDB中使用聚合获得每月的项目数。
我正在使用mongodb，我想显示一个月内购买的商品数量。我想在服务层使用聚合。
这是我的控制器

@GetMapping("/demo")
    public List<Order> demo(@Param(value = "date") String date){

        Aggregation agg = newAggregation(
                project("date").and(DateOperators.Month.month("date")).as("month"),
                group("month").count().as("count"),
                project("count").and("month").previousOperation(),
                sort(ASC, "count")
        );

        AggregationResults<Order> results = mongoTemplate.aggregate(agg,
                "order", Order.class);
        List<Order> joinCount = results.getMappedResults();
        return joinCount;
    }

当我执行此api时：http://localhost：8080/demo？date=22/04/2020然后我得到以下错误：

com.mongodb.MongoCommandException: Command failed with error 16006 (Location16006): 'Failed to optimize pipeline :: caused by :: can't convert from BSON type string to Date' on server localhost:27017. The full response is {"ok": 0.0, "errmsg": "Failed to optimize pipeline :: caused by :: can't convert from BSON type string to Date", "code": 16006, "codeName": "Location16006"}
    at com.mongodb.internal.connection.ProtocolHelper.getCommandFailureException(ProtocolHelper.java:175) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.internal.connection.InternalStreamConnection.receiveCommandMessageResponse(InternalStreamConnection.java:359) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.internal.connection.InternalStreamConnection.sendAndReceive(InternalStreamConnection.java:280) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.internal.connection.UsageTrackingInternalConnection.sendAndReceive(UsageTrackingInternalConnection.java:100) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.internal.connection.DefaultConnectionPool$PooledConnection.sendAndReceive(DefaultConnectionPool.java:490) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.internal.connection.CommandProtocolImpl.execute(CommandProtocolImpl.java:71) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.internal.connection.DefaultServer$DefaultServerProtocolExecutor.execute(DefaultServer.java:255) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.internal.connection.DefaultServerConnection.executeProtocol(DefaultServerConnection.java:202) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.internal.connection.DefaultServerConnection.command(DefaultServerConnection.java:118) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.internal.connection.DefaultServerConnection.command(DefaultServerConnection.java:110) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.internal.operation.CommandOperationHelper.executeCommand(CommandOperationHelper.java:345) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.internal.operation.CommandOperationHelper.executeCommand(CommandOperationHelper.java:336) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.internal.operation.CommandOperationHelper.executeCommandWithConnection(CommandOperationHelper.java:222) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.internal.operation.CommandOperationHelper$5.call(CommandOperationHelper.java:208) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.internal.operation.OperationHelper.withReadConnectionSource(OperationHelper.java:582) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.internal.operation.CommandOperationHelper.executeCommand(CommandOperationHelper.java:205) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.internal.operation.AggregateOperationImpl.execute(AggregateOperationImpl.java:189) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.internal.operation.AggregateOperation.execute(AggregateOperation.java:296) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.internal.operation.AggregateOperation.execute(AggregateOperation.java:41) ~[mongodb-driver-core-4.1.1.jar:na]
    at com.mongodb.client.internal.MongoClientDelegate$DelegateOperationExecutor.execute(MongoClientDelegate.java:178) ~[mongodb-driver-sync-4.1.1.jar:na]
    at com.mongodb.client.internal.MongoIterableImpl.execute(MongoIterableImpl.java:135) ~[mongodb-driver-sync-4.1.1.jar:na]
    at com.mongodb.client.internal.MongoIterableImpl.iterator(MongoIterableImpl.java:92) ~[mongodb-driver-sync-4.1.1.jar:na]
    at com.mongodb.client.internal.MongoIterableImpl.forEach(MongoIterableImpl.java:121) ~[mongodb-driver-sync-4.1.1.jar:na]
    at com.mongodb.client.internal.MappingIterable.forEach(MappingIterable.java:59) ~[mongodb-driver-sync-4.1.1.jar:na]
    at com.mongodb.client.internal.MappingIterable.into(MappingIterable.java:69) ~[mongodb-driver-sync-4.1.1.jar:na]
    at org.springframework.data.mongodb.core.MongoTemplate.lambda$doAggregate$25(MongoTemplate.java:2173) ~[spring-data-mongodb-3.1.1.jar:3.1.1]
    at org.springframework.data.mongodb.core.MongoTemplate.execute(MongoTemplate.java:562) ~[spring-data-mongodb-3.1.1.jar:3.1.1]
    at org.springframework.data.mongodb.core.MongoTemplate.doAggregate(MongoTemplate.java:2130) ~[spring-data-mongodb-3.1.1.jar:3.1.1]
    at org.springframework.data.mongodb.core.MongoTemplate.aggregate(MongoTemplate.java:2099) ~[spring-data-mongodb-3.1.1.jar:3.1.1]
    at org.springframework.data.mongodb.core.MongoTemplate.aggregate(MongoTemplate.java:1998) ~[spring-data-mongodb-3.1.1.jar:3.1.1]
    at com.example.product.controller.OrderController.demo1(OrderController.java:74) ~[classes/:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:564) ~[na:na]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:197) ~[spring-web-5.3.1.jar:5.3.1]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:141) ~[spring-web-5.3.1.jar:5.3.1]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) ~[spring-webmvc-5.3.1.jar:5.3.1]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:893) ~[spring-webmvc-5.3.1.jar:5.3.1]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:807) ~[spring-webmvc-5.3.1.jar:5.3.1]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.1.jar:5.3.1]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1061) ~[spring-webmvc-5.3.1.jar:5.3.1]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:961) ~[spring-webmvc-5.3.1.jar:5.3.1]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.1.jar:5.3.1]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.3.1.jar:5.3.1]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:626) ~[tomcat-embed-core-9.0.39.jar:4.0.FR]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.1.jar:5.3.1]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) ~[tomcat-embed-core-9.0.39.jar:4.0.FR]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.39.jar:9.0.39]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.1.jar:5.3.1]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.1.jar:5.3.1]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.1.jar:5.3.1]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.1.jar:5.3.1]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.1.jar:5.3.1]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.3.1.jar:5.3.1]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) [tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) [tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) [tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) [tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374) [tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) [tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590) [tomcat-embed-core-9.0.39.jar:9.0.39]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.39.jar:9.0.39]
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167) [na:na]
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641) [na:na]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.39.jar:9.0.39]
    at java.base/java.lang.Thread.run(Thread.java:844) [na:na]

我如何计算每月和每年的订单数量？