private String contrast() {
        final MetaDataDO before = (MetaDataDO) getBefore();
        Objects.requireNonNull(before);
        final MetaDataDO after = (MetaDataDO) getAfter();
        Objects.requireNonNull(after);
        if (Objects.equals(before, after)) {
            return "it no change";
        }
        final StringBuilder builder = new StringBuilder();
        if (!Objects.equals(before.getAppName(), after.getAppName())) {
            builder.append(String.format("appName[%s => %s] ", before.getAppName(), after.getAppName()));
        }
        if (!Objects.equals(before.getPath(), after.getPath())) {
            builder.append(String.format("path[%s => %s] ", before.getPath(), after.getPath()));
        }
        if (!Objects.equals(before.getPathDesc(), after.getPathDesc())) {
            builder.append(String.format("path desc[%s => %s] ", before.getPathDesc(), after.getPathDesc()));
        }
        if (!Objects.equals(before.getServiceName(), after.getServiceName())) {
            builder.append(String.format("service[%s => %s] ", before.getServiceName(), after.getServiceName()));
        }
        if (!Objects.equals(before.getMethodName(), after.getMethodName())) {
            builder.append(String.format("method[%s => %s] ", before.getMethodName(), after.getMethodName()));
        }
        if (!Objects.equals(before.getParameterTypes(), after.getParameterTypes())) {
            builder.append(String.format("parameter type[%s => %s] ", before.getParameterTypes(), after.getParameterTypes()));
        }
        if (!Objects.equals(before.getEnabled(), after.getEnabled())) {
            builder.append(String.format("enable[%s => %s] ", before.getEnabled(), after.getEnabled()));
        }
        if (!Objects.equals(before.getRpcType(), after.getRpcType())) {
            builder.append(String.format("rpc type[%s => %s] ", before.getRpcType(), after.getRpcType()));
        }
        if (!Objects.equals(before.getRpcExt(), after.getRpcExt())) {
            builder.append(String.format("rpc ext[%s => %s] ", before.getRpcExt(), after.getRpcExt()));
        }
        return builder.toString();
    }
Create a new {@code PluginChangedEvent}.operator is unknown.

@param source   Current plugin state
@param before   Before the change plugin state
@param type     event type
@param operator operator
shenyu-admin/src/main/java/org/apache/shenyu/admin/model/event/metadata/MetaDataChangedEvent.java