RestEasy：org.codehaus.jackson.map.JsonMappingException：无法从START_OBJECT令牌（..）中反序列化java.util.ArrayList的实例。

Question

我有一个休息终点，它返回List<VariablePresentation>。我正在尝试将此其余端点测试为

    @Test
    public void testGetAllVariablesWithoutQueryParamPass() throws Exception {
        final ClientRequest clientCreateRequest = new ClientRequest("http://localhost:9090/variables");
        final MultivaluedMap<String, String> formParameters = clientCreateRequest.getFormParameters();
        final String name = "testGetAllVariablesWithoutQueryParamPass";
        formParameters.putSingle("name", name);
        formParameters.putSingle("type", "String");
        formParameters.putSingle("units", "units");
        formParameters.putSingle("description", "description");
        formParameters.putSingle("core", "true");

        final GenericType<List<VariablePresentation>> typeToken = new GenericType<List<VariablePresentation>>() {
        };
        final ClientResponse<List<VariablePresentation>> clientCreateResponse = clientCreateRequest.post(typeToken);
        assertEquals(201, clientCreateResponse.getStatus());
        final List<VariablePresentation> variables = clientCreateResponse.getEntity();
        assertNotNull(variables);
        assertEquals(1, variables.size());

    }

该测试失败，错误提示

org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of java.util.ArrayList out of START_OBJECT token(..)

如何解决此问题？

Answer 1

这看起来像杰克逊（Jackson）错误，它期望解析一个数组（以“ [”开头），但遇到一个对象（“
{”）的开头标记。通过查看您的代码，我猜测它正在尝试将JSON反序列化到您的List中，但它正在获取对象的JSON。

您的REST端点返回的JSON是什么样的？它应该看起来像这样

[
    {
        // JSON for VariablePresentation value 0
        "field0": <some-value>
        <etc...>
    },
    <etc...>
]