如何使用@ResponseBody从spring Controller返回JSON数据

Question

Spring版本4.2.0,Hibernate 4.1.4 这是我的Controller功能:

@RequestMapping(value = "/mobile/getcomp", method = RequestMethod.GET)
@ResponseBody
public List<Company>  listforCompanies() {      
    List<Company> listOfCompanies= new ArrayList<Company>();        
    listOfCompanies = companyManager.getAllCompanies();
    return listOfCompanies;
}

杰克逊JSON映射器依赖Pom.xml:

    <!-- Jackson JSON Mapper -->
    <dependency>
        <groupId>org.codehaus.jackson</groupId>
        <artifactId>jackson-mapper-asl</artifactId>
        <version>${jackson.version}</version>
    </dependency>

获取列表ArrayList,但返回时会显示以下错误:

SEVERE: Servlet.service() for servlet [dispatcherServlet] in context with path [/IrApp] threw exception [Request processing failed; nested exception is java.lang.IllegalArgumentException: No converter found for return value of type: class java.util.ArrayList] with root cause
    java.lang.IllegalArgumentException: No converter found for return value of type: class java.util.ArrayList
        at org.springframework.util.Assert.isTrue(Assert.java:68)
        at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:124)

链接到我正在关注的示例.

Answer 1

将以下依赖项添加到您的pom.xml:

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.5.0</version>
</dependency>

Answer 2

我面临同样的问题.@ResponseBody自从我使用以来我没有放过@RestController.但我仍然遇到错误,因为我没有把getter/setter方法用于公司类.所以在把getter/setter我的问题解决后.

Answer 3

您还需要确保返回的bean不为空(并且可以由Jackson序列化).在我的特殊情况下,我尝试返回一个没有getter和setter的对象实例,没有任何jackson注释,并且字段等于null.我得到以下消息:

com.fasterxml.jackson.databind.JsonMappingException:
    No serializer found for class com.foo.bar.Baz and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) )

Answer 4

当我遇到这个问题时,我只是简单地使用getter setter方法,我的问题就解决了.

我使用的是Spring启动版2.0.

Answer 5

考虑到@Arpit的回答，对我来说，只有当我添加两个杰克逊依赖项时它才有效：

<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>

当然，还配置了 web.xml <mvc:annotation-driven/>。

对我有帮助的原始答案在这里：https ://stackoverflow.com/a/33896080/3014866