java.lang.IllegalArgumentException

原因：请求返回的数据无法转换，需要添加如下配置：

<dependency>  
    <groupId>com.fasterxml.jackson.core</groupId>  
    <artifactId>jackson-core</artifactId>  
    <version>2.4.3</version>  
</dependency>  
<dependency>  
    <groupId>com.fasterxml.jackson.core</groupId>  
    <artifactId>jackson-databind</artifactId>  
    <version>2.4.3</version>  
</dependency>