春季Json反序列化問題3.2.0

Question

我在使用Spring 3.2.0和Jackson 2.1.1反序列化對象數組時遇到問題。 當我點擊控制器與對象數組它拋出「無法實例化bean類。沒有默認構造函數找到」。我的Pojo也有默認的構造函數。我正在使用MappingJackson2HttpMessageConverter在調度程序 - 小服務程序中進行JSON處理。

POJO的：

public class Student{ 

    private String rollNum; 
    private String firstName; 
    private String lastName; 

      public Student(){ 

      } 

    /** 
    * @return the firstName 
    */ 
    public String getFirstName() { 
     return firstName; 
    } 
    /** 
    * @param firstName the firstName to set 
    */ 
    public void setFirstName(String firstName) { 
     this.firstName = firstName; 
    } 
    /** 
    * @return the lastName 
    */ 
    public String getLastName() { 
     return lastName; 
    } 
    /** 
    * @param lastName the lastName to set 
    */ 
    public void setLastName(String lastName) { 
     this.lastName = lastName; 
    } 
    /** 
    * @return the rollNum 
    */ 
    public String getRollNum() { 
     return rollNum; 
    } 
    /** 
    * @param rollNum the rollNum to set 
    */ 
    public void setRollNum(String rollNum) { 
     this.rollNum = rollNum; 
    } 
} 

控制器類：

public @ResponseBody 
String saveStudentName(
     final @ModelAttribute Student[] student){ 

     //code goes here 

    } 

該服務由iOS應用程序擊中。當我用單個對象（@ModelAttribute Student學生）打相同的服務時，它工作正常。但是，隨着對象的數組擊中，它會拋出異常，因爲

org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [[Lcom.student.pojo.Student;]: No default constructor found; 

客戶端輸入

[{"rollNum":"12","firstName":"qweqw","lastName":"adsf"},{"rollNum":"23","firstName":"rty","lastName":"fghj"}] 

和客戶端獲取下面的錯誤作爲響應

Error Domain=NSCocoaErrorDomain Code=3840 "The operation couldn’t be completed. (Cocoa error 3840.)" (Invalid value around character 0.) UserInfo=0x7522680 {NSDebugDescription=Invalid value around character 0.} 

請一些人告訴在哪裏錯了。如果控制器參數正確，請告訴我可以發送給控制器的輸入格式。

在此先感謝。

Answer 1

首先，你必須圍繞學生的這樣的列表中創建一個包裝：

class Students extends ArrayList<Student> { 
    public Students() { 
     super(); 
    } 
    } 

也改變了服務方式是這樣的：

public @ResponseBody String saveStudentName(final @ModelAttribute Students students){ 

     //code goes here 

    } 

我想這將解決您的問題。

〜Ragesh AK

Answer 2

Below are the complete configs: 

**My 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/maven-v4_0_0.xsd"> 
    <modelVersion>4.0.0</modelVersion> 
    <groupId>com.springframework.rest</groupId> 
    <artifactId>RestWebService</artifactId> 
    <packaging>war</packaging> 
    <version>1.0-SNAPSHOT</version> 
    <name>RestWebService Maven Webapp</name> 
    <url>http://maven.apache.org</url> 
    <properties> 
    <spring.version>3.0.5.RELEASE</spring.version> 
    <junit.version>4.11</junit.version> 
    <jdk.version>1.6</jdk.version> 
    </properties> 
    <dependencies> 
    <!-- Spring 3 dependencies --> 
    <dependency> 
     <groupId>org.springframework</groupId> 
     <artifactId>spring-core</artifactId> 
     <version>${spring.version}</version> 
    </dependency> 
    <dependency> 
     <groupId>org.springframework</groupId> 
     <artifactId>spring-web</artifactId> 
     <version>${spring.version}</version> 
    </dependency> 
    <dependency> 
     <groupId>org.springframework</groupId> 
     <artifactId>spring-webmvc</artifactId> 
     <version>${spring.version}</version> 
    </dependency> 
    <dependency> 
     <groupId>org.codehaus.jackson</groupId> 
     <artifactId>jackson-mapper-asl</artifactId> 
     <version>1.9.7</version> 
     <scope>compile</scope> 
    </dependency> 
    <!-- dependency> 
     <groupId>org.springframework.integration</groupId> 
     <artifactId>spring-integration-stream</artifactId> 
     <version>2.1.3.RELEASE</version> 
    </dependency --> 

    <dependency> 
     <groupId>junit</groupId> 
     <artifactId>junit</artifactId> 
     <version>${junit.version}</version> 
     <scope>test</scope> 
    </dependency> 
    </dependencies> 
    <build> 
    <finalName>RestWebService</finalName> 
    <plugins> 
     <plugin> 
      <groupId>org.apache.maven.plugins</groupId> 
      <artifactId>maven-compiler-plugin</artifactId> 
      <version>3.0</version> 
      <configuration> 
       <source>${jdk.version}</source> 
       <target>${jdk.version}</target> 
      </configuration> 
     </plugin> 
    </plugins> 
    </build> 
</project> 

**dispatcher-servlet.xml:** 

<?xml version="1.0" encoding="UTF-8"?> 
<beans xmlns="http://www.springframework.org/schema/beans" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" 
    xsi:schemaLocation=" 
     http://www.springframework.org/schema/beans 
     http://www.springframework.org/schema/beans/spring-beans-3.0.xsd 
     http://www.springframework.org/schema/context 
     http://www.springframework.org/schema/context/spring-context-3.0.xsd"> 

    <context:component-scan base-package="com.springframework.rest" /> 
    <!-- To enable @RequestMapping process on type level and method level --> 
    <bean class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping" /> 
    <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"> 
     <property name="messageConverters"> 
      <list>    
       <ref bean="jsonConverter" /> 
      </list> 
     </property> 
    </bean> 

    <bean id="jsonConverter" class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter"> 
     <property name="supportedMediaTypes" value="application/json" /> 
    </bean> 
</beans> 


**Student:** 

public class Student { 
    private String name; 
    private int id; 
    private String address; 


    public Student() { 

    } 

    public Student(int id, String name, String address) { 
     this.id = id; 
     this.name = name; 
     this.address = address; 
    } 

    public String getName() { 
     return name; 
    } 

    public void setName(String name) { 
     this.name = name; 
    } 

    public int getId() { 
     return id; 
    } 

    public void setId(int id) { 
     this.id = id; 
    } 

    public String getAddress() { 
     return address; 
    } 

    public void setAddress(String address) { 
     this.address = address; 
    } 



} 

**Students:** 

public class Students extends ArrayList<Student> { 

    public Students() { 
     super(); 
    } 

} 

**Controller:** 

@Controller 
public class BaseController{  

    @RequestMapping(value="/student", method = RequestMethod.POST) 
    @ResponseBody 
    public String saveStudent(@RequestBody Students students) { 
     System.out.println("Size:"+students.size()); 
     return "Success"; 
    } 

} 

請讓我知道如果這能幫助你....