我有本地托管的Web服务。控制器返回单个String值时可以正常工作。但是,每当我尝试返回列表或特定对象时,它都会返回带有错误代码500的Whitelabel错误页面。以下是我尝试返回列表时的错误。
发生意外错误(类型=内部服务器错误,状态= 500)。
未找到类型为返回值的转换器:类java.util.Arrays $ ArrayList
当我尝试访问特定对象(例如/ topic / 1)时,出现以下错误。
发生意外错误(类型=内部服务器错误,状态= 500)。
找不到类型为com.spring.rest.topic.Topic的返回值的转换器
注意:1.我看到jackson依赖是由spring-boot-starter-web依赖添加的。因此,不需要再次在pom.xml中添加。
2.我的Pojo课程Topic拥有所有属性的公共获取器。
以下是我的课程:
Topic.java(Pojo类):
package com.spring.rest.topic;
public class Topic {
private String id;
private String name;
private String description;
public Topic(){
}
public Topic(String id, String name, String description) {
super();
this.id = id;
this.name = name;
this.description = description;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
TopicController.java(Controller类):
package com.spring.rest.topic;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class TopicController {
@Autowired //this annotation tells spring to inject an object for the dependency.
private TopicService service;
@RequestMapping("/topics") //spring mvc casts the list to json.
public List<Topic> getAllTopics(){
return service.getAllTopics();
}
@RequestMapping("/topic/{id}")
public Topic getTopic(@PathVariable String id){
return service.getTopic(id);
}
}
TopicService.java(Service class):
package com.spring.rest.topic;
import java.util.Arrays;
import java.util.List;
import org.springframework.stereotype.Service;
//in spring, a service class is of singleton scope.
@Service
public class TopicService {
private List<Topic> topics = Arrays.asList(new Topic("1","SpringMVC","Using spring mvc"),
new Topic("2","RESTful API","Using REST top create a micro services"));
public List<Topic> getAllTopics(){
return topics;
}
public Topic getTopic(String id){
/*Topic topic = new Topic();*/
for(Topic topic : getAllTopics()){
if(topic.getId().equals(id)){
return topic;
}
}
return null;
}
}
pom.xml:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>spring.java.rest.demo</groupId>
<artifactId>SpringRest</artifactId>
<version>0.0.1-SNAPSHOT</version>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.4.2.RELEASE</version>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
</dependencies>
<properties>
<java-version>1.8</java-version>
</properties>
</project>
最佳答案
您需要在依赖关系树中包含一个json映射器,例如com.fasterxml.jackson.core
的jackson-databind
。即
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.8.8</version>
</dependency>