我正在使用Spring的RestTemplate来使用Chargify API，使用JSON作为有效负载格式。它一直很顺利，但是当我尝试获取一系列对象时，它失败了。例如，请考虑以下事项：
Transaction[] transactions = restTemplate.getForObject(
CHARGIFY_ENDPOINT + "/subscriptions/{subscription}/transactions.json",
Transaction[].class,
subscriptionId
);
实际的GET很好，JSON响应为：
[ { "transaction" : { "amount_in_cents" : 3006,
"created_at" : "2012-06-17T16:32:05-04:00",
"ending_balance_in_cents" : 0,
"id" : 17283728,
"kind" : null,
"memo" : "",
"payment_id" : null,
"product_id" : 120387,
"subscription_id" : 1947292,
"success" : true,
"transaction_type" : "payment",
"type" : "Payment"
} },
{ "transaction" : { "amount_in_cents" : 5900,
"created_at" : "2012-06-17T16:32:05-04:00",
"ending_balance_in_cents" : 3006,
"id" : 17283727,
"kind" : "baseline",
"memo" : "Professional Plan (06/17/2012 - 07/17/2012)",
"payment_id" : 17283728,
"product_id" : 120387,
"subscription_id" : 1947292,
"success" : true,
"transaction_type" : "charge",
"type" : "Charge"
} },
{ "transaction" : { "amount_in_cents" : -2894,
"created_at" : "2012-06-17T16:32:03-04:00",
"ending_balance_in_cents" : -2894,
"id" : 17283726,
"kind" : "prorated",
"memo" : "",
"payment_id" : null,
"product_id" : 120387,
"subscription_id" : 1947292,
"success" : null,
"transaction_type" : "adjustment",
"type" : "Adjustment"
} },
{ "transaction" : { "amount_in_cents" : 2900,
"created_at" : "2012-06-17T15:17:07-04:00",
"ending_balance_in_cents" : 0,
"id" : 17281084,
"kind" : null,
"memo" : "",
"payment_id" : null,
"product_id" : 120386,
"subscription_id" : 1947292,
"success" : true,
"transaction_type" : "payment",
"type" : "Payment"
} },
{ "transaction" : { "amount_in_cents" : 2900,
"created_at" : "2012-06-17T15:17:06-04:00",
"ending_balance_in_cents" : 2900,
"id" : 17281083,
"kind" : "baseline",
"memo" : "Standard Plan (06/17/2012 - 07/17/2012)",
"payment_id" : 17281084,
"product_id" : 120386,
"subscription_id" : 1947292,
"success" : true,
"transaction_type" : "charge",
"type" : "Charge"
} }
]
但是，当Jackson尝试反序列化JSON时，会产生JsonMappingException: Current token not START_OBJECT (needed to unwrap root name 'Transaction[]'), but START_ARRAY：
16:59:12.651 [http-8080-1] DEBUG org.springframework.web.client.RestTemplate - GET request for "https://foobar.chargify.com/subscriptions/1947292/transactions.json" resulted in 200 (OK)
16:59:12.651 [http-8080-1] DEBUG org.springframework.web.client.RestTemplate - Reading [[Lcom.foobar.chargify.Transaction;] as "application/json;charset=utf-8" using [org.springframework.http.converter.json.MappingJacksonHttpMessageConverter@1ea8dbd]
16:59:12.662 [http-8080-1] DEBUG org.apache.http.wire - << "[{"transaction":{"type":"Payment","amount_in_cents":3006,"payment_id":null,"memo":"","id":17283728,"created_at":"2012-06-17T16:32:05-04:00","subscription_id":1947292,"kind":null,"ending_balance_in_cents":0,"success":true,"product_id":120387,"transaction_type":"payment"}},{"transaction":{"type":"Charge","amount_in_cents":5900,"payment_id":17283728,"memo":"Professional Plan (06/17/2012 - 07/17/2012)","id":17283727,"created_at":"2012-06-17T16:32:05-04:00","subscription_id":1947292,"kind":"baseline","ending_balance_in_cents":3006,"success":true,"product_id":120387,"transaction_type":"charge"}},{"transaction":{"type":"Adjustment","amount_in_cents":-2894,"payment_id":null,"memo":"","id":17283726,"created_at":"2012-06-17T16:32:03-04:00","subscription_id":1947292,"kind":"prorated","ending_balance_in_cents":-2894,"success":null,"product_id":120387,"transaction_type":"adjustment"}},{"transaction":{"type":"Payment","amount_in_cents":2900,"payment_id":null,"memo":"","id":17281084,"created_at":"2012-06-17T15:17:07-04:00","subscription_id":1947292,"kind":null,"ending_balance_in_cents":0,"success":true,"product_id":120386,"transaction_type":"payment"}},{"transaction":{"type":"Charge","amount_in_cents":2900,"payment_id":17281084,"memo":"Standard Plan (06/17/2012 - 07/17/2012)","id":17281083,"created_at":"2012-06-17T15:17:06-04:00","subscription_id":1947292,"kind":"baseline","ending_balance_in_cents":2900,"success":true,"product_id":120386,"transaction_type":"charge"}}]"
16:59:12.683 [http-8080-1] DEBUG org.apache.http.impl.conn.SingleClientConnManager - Releasing connection org.apache.http.impl.conn.SingleClientConnManager$ConnAdapter@17ed710
16:59:12.684 [http-8080-1] DEBUG org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver - Resolving exception from handler [public void com.foobar.controllers.TestController.viewTransactions(int)]: org.springframework.http.converter.HttpMessageNotReadableException: Could not read JSON: Current token not START_OBJECT (needed to unwrap root name 'Transaction[]'), but START_ARRAY
at [Source: org.apache.http.conn.EofSensorInputStream@598a5d; line: 1, column: 1]; nested exception is org.codehaus.jackson.map.JsonMappingException: Current token not START_OBJECT (needed to unwrap root name 'Transaction[]'), but START_ARRAY
at [Source: org.apache.http.conn.EofSensorInputStream@598a5d; line: 1, column: 1]
16:59:12.686 [http-8080-1] DEBUG org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver - Resolving exception from handler [public void com.foobar.controllers.TestController.viewTransactions(int)]: org.springframework.http.converter.HttpMessageNotReadableException: Could not read JSON: Current token not START_OBJECT (needed to unwrap root name 'Transaction[]'), but START_ARRAY
at [Source: org.apache.http.conn.EofSensorInputStream@598a5d; line: 1, column: 1]; nested exception is org.codehaus.jackson.map.JsonMappingException: Current token not START_OBJECT (needed to unwrap root name 'Transaction[]'), but START_ARRAY
at [Source: org.apache.http.conn.EofSensorInputStream@598a5d; line: 1, column: 1]
16:59:12.686 [http-8080-1] DEBUG org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver - Resolving exception from handler [public void com.foobar.controllers.TestController.viewTransactions(int)]: org.springframework.http.converter.HttpMessageNotReadableException: Could not read JSON: Current token not START_OBJECT (needed to unwrap root name 'Transaction[]'), but START_ARRAY
at [Source: org.apache.http.conn.EofSensorInputStream@598a5d; line: 1, column: 1]; nested exception is org.codehaus.jackson.map.JsonMappingException: Current token not START_OBJECT (needed to unwrap root name 'Transaction[]'), but START_ARRAY
at [Source: org.apache.http.conn.EofSensorInputStream@598a5d; line: 1, column: 1]
我之前和杰克逊讨论过这个问题，经过几天的研究后，我最终选择了不同的路线。这次不是一个选择，我没有运气找出解决方案。
有什么想法吗？如果我得到一个数组或List，我不在乎。我也没有运气。
在阅读杰克逊的文档时，我看到了你应该能够包装列表的地方，即new TypeReference<List<Transaction>>()，但我也没有运气。
BTW，由于Chargify如何格式化他们的JSON响应，我的RestTemplate配置了自定义ObjectMapper来设置这些选项：
configure(SerializationConfig.Feature.WRAP_ROOT_VALUE, true);
configure(DeserializationConfig.Feature.UNWRAP_ROOT_VALUE, true);
当我删除这些选项时，不会抛出JsonMappingException，但生成的Transaction对象的所有字段都为空。
我也尝试添加此选项，但似乎没有帮助：
configure(DeserializationConfig.Feature.USE_JAVA_ARRAY_FOR_JSON_ARRAY, true);
答案 0 :(得分：3)
你只需要在Transaction之上另一个包装类型，也请删除UNWRAP_ROOT_VALUE选项。
这些课程将按以下方式进行：
public class TransactionHolder {
private Transaction transaction;
...
}
public class Transaction {
private String amount_in_cents;
private String created_at;
private int ending_balance_in_cents;
private int id;
private String kind;
private String memo;
private int payment_id;
private int product_id;
private int subscription_id;
private boolean success;
private String transaction_type;
private String type;
...
}
使用您的样本json，以下内容适合我：
ObjectMapper mapper = new ObjectMapper();
InputStream is = this.getClass().getResourceAsStream("sample.json");
TransactionHolder[] holders = mapper.readValue(is,TransactionHolder[].class);