关于WebSocketSession传输JSON

痛定思痛。 2022-01-23 22:47 206阅读 0赞

由于约定需要向前端传输JSON，但是之前调用的一直是WebSocketSession自带的sendMessage()方法。方法签名如下：

void sendMessage(WebSocketMessage<?> var1) throws IOException;

所以在sendMessage()中是不能直接发送JSON的，必须是发送实现了WebSocketMessage接口的类型的对象，接口定义如下：

package org.springframework.web.socket;
    
    public interface WebSocketMessage<T> {
        T getPayload();
    
        int getPayloadLength();
    
        boolean isLast();
    }

TextMessage类继承了抽象类AbstractWebSocketSocketMessage(实现了WebSocketMessage接口)

//
    // Source code recreated from a .class file by IntelliJ IDEA
    // (powered by Fernflower decompiler)
    //
    
    package org.springframework.web.socket;
    
    import java.nio.charset.Charset;
    
    public final class TextMessage extends AbstractWebSocketMessage<String> {
        private static final Charset UTF8_CHARSET = Charset.forName("UTF-8");
        private final byte[] bytes;
    
        public TextMessage(CharSequence payload) {
            super(payload.toString(), true);
            this.bytes = null;
        }
    
        public TextMessage(byte[] payload) {
            super(new String(payload, UTF8_CHARSET));
            this.bytes = payload;
        }
    
        public TextMessage(CharSequence payload, boolean isLast) {
            super(payload.toString(), isLast);
            this.bytes = null;
        }
    
        public int getPayloadLength() {
            return this.asBytes().length;
        }
    
        public byte[] asBytes() {
            return this.bytes != null ? this.bytes : ((String)this.getPayload()).getBytes(UTF8_CHARSET);
        }
    
        protected String toStringPayload() {
            String payload = (String)this.getPayload();
            return payload.length() > 10 ? payload.substring(0, 10) + ".." : payload;
        }
    }

所以TextMessage通常只用来传输字符串或者byte\[\]，这时候考虑了对json序列化，然后考虑到效率，觉得不如直接用toString()来的好，所以在有需要传输json的场景则直接创建一个JSONObject 然后转换字符串传输就好。