@Test
    public void testSPIGetJoinNameIsBlank() {
        try {
            ExtensionLoader.getExtensionLoader(JdbcSPI.class).getJoin("");
            fail();
        } catch (NullPointerException expected) {
            assertThat(expected.getMessage(), containsString("get join name is null"));
        }
    }
test ExtensionLoader.getJoin() blank name param case.
shenyu-spi/src/test/java/org/apache/shenyu/spi/ExtensionLoaderTest.java