private List<Map<String, String>> messages = new ArrayList<Map<String, String>>() {{
        add(new HashMap<String, String>() {{
            put("id", "1");
            put("text", "First message");
        }});
        add(new HashMap<String, String>() {{
            put("id", "2");
            put("text", "Second message");
        }});
        add(new HashMap<String, String>() {{
            put("id", "3");
            put("text", "Third message");
        }});
    }};

    @GetMapping
    public List<Map<String, String>> list() {
        return messages;
    }