@destinationvariable未找到转换器

Question

@MessageMapping("/chat/{usersSelected}")
public void disperseMessage(@DestinationVariable("usersSelected") List<UserSelected> usersSelected) {...

客户端对象如下所示：

vm.usersSelected = [];

var userSelected = {};
userSelected.userId = userId;
userSelected.institutionId = institutionId;
vm.usersSelected.push(userSelected);

我得到以下异常：

org.springframework.core.convert.converterNotFoundException：找不到能够从java.lang.String类型转换为@org.springframework.messaging.handler.annotation.destinationvariable java.util.list类型的转换器

vm.stompClient.send("/app/chat/" + vm.institutionIdOfSender + "/" + vm.userIdOfSender + "/" + vm.usersSelected + "/" + confirmation, {}, JSON.stringify({ 'name': vm.name, 'id': vm.userIdOfSender, 'message': message }));

@MessageMapping("/chat/{institutionIdOfSender}/{userIdOfSender}/{usersSelected}/{confirmation}")
public void disperseMessage(@DestinationVariable("institutionIdOfSender") String institutionIdOfSender,
        @DestinationVariable("userIdOfSender") String userIdOfSender, @DestinationVariable("usersSelected") String usersSelected,
        @DestinationVariable("confirmation") Boolean confirmation, final ChatMessage message) throws Exception {

    @MessageMapping("/chat/{institutionIdOfSender}/{userIdOfSender}/{usersSelected}/{confirmation}/{chatMessageFilter}")
public void disperseMessage(@DestinationVariable("institutionIdOfSender") String institutionIdOfSender,
        @DestinationVariable("userIdOfSender") String userIdOfSender, @DestinationVariable("usersSelected") String usersSelectedString,
        @DestinationVariable("confirmation") Boolean confirmation,
        @DestinationVariable("chatMessageFilter") ChatMessageFilterEnum chatMessageFilter, final ChatMessage message) throws Exception {

    // transfer JSON- string into List- Objects:
    final List<UserSelected> usersSelected = new ObjectMapper().readValue(usersSelectedString,
        new TypeReference<List<UserSelected>>() {});

vm.stompClient.send("/app/chat/" + vm.institutionIdOfSender + "/" + vm.userIdOfSender + "/" + JSON.stringify(vm.usersSelected) + "/" + confirmation + "/SELECTED_USERS", {}, JSON.stringify({ 'name': vm.name, 'id': vm.userIdOfSender, 'message': message }));

我有机会不在服务器上自己转换JSON字符串吗？（这个应该在场景后面做）谢谢你的帮助！

Answer 1

@destinationvariable不引用消息的正文，而是路径中字符串的占位符。

例如（使用与代码相同的模式）

@MessageMapping("/chat/{chatChannel}")
public void disperseMessage(@DestinationVariable("chatChannel") String chatChannel) {...

如果我要向/chat/allchat发送消息，chatChannel的值将是字符串“allchat”

因此，这个错误的意思是它不能将字母“AllChat”转换为列表，因为“AllChat”将不是足够的信息（除非您创建了一个转换器，从一个频道中获取用户列表，这可能不是您想要的，而且作为一项服务可能更有意义）

http://docs.spring.io/spring/docs/current/spring-framework-reference/html/websocket.html

IO有一个关于WebSockets的很棒的Spring Boot教程，该教程展示了一个示例服务，该服务的消息体应该使用可用的json解析器。所以我只是调整了教程中的代码以适合您。

JavaScript

var message = {
    'chatMessage': { 'name': vm.name, 'id': vm.userIdOfSender, 'message': message },
    'usersSelected': vm.usersSelected
}
vm.stompClient.send("/app/chat/" + vm.institutionIdOfSender + "/" + vm.userIdOfSender + "/" + confirmation + "/SELECTED_USERS", {}, JSON.stringify(message));

Java-可以随意将类命名为ChatMessageAndUsersSelected更好的名称

import org.springframework.messaging.handler.annotation.MessageMapping;
import org.springframework.messaging.handler.annotation.SendTo;
import org.springframework.stereotype.Controller;

@Controller
public class GreetingController {


    @MessageMapping("/chat/{institutionIdOfSender}/{userIdOfSender}/{usersSelected}/{confirmation}/{chatMessageFilter}")
    public void disperseMessage(@DestinationVariable("institutionIdOfSender") String institutionIdOfSender,
        @DestinationVariable("userIdOfSender") String userIdOfSender,
        @DestinationVariable("confirmation") Boolean confirmation, final ChatMessageAndUsersSelected message) throws Exception {
        //Do stuff here.
    }

}