jQuery post can't get entity object as json - json

Question

I need to get my 'Comment' (stored in DAO) object from my controller and display it in my JSP but every time I see the error message from the error block.
Why is this happenning and what should I do?
Logic of my code is the next:
After clicking on the 'Reply' button data from the form is sent to my controller.
Controller saves data in DB and returns 'Comment' entity.
I get this 'Comment' entity in my JSP page and use it for publishing on the page.
But I get the error msg from error block instead of msg from the success block.
Here is my form:
<form id="comment_${comment.getCommentId()}">
<textarea class="textarea" rows="10" name="text"></textarea>
<input type="hidden" name="bookId" value="${book.getBookId()}" />
<input type="hidden" name="parentId" />
<input type="hidden" name="commentId" value="${comment.getCommentId()}" /><br />
<input type="button" class="button" value="Reply" id="submit_${comment.getCommentId()}" onclick="ajaxsubmit(this.id)"/>
</form>
Here is my script:
<script type="text/javascript">
function ajaxsubmit(buttonId){
var formId = document.getElementById(buttonId).parentNode.id;
var dataString = $("#" + formId).serialize();
$.ajax( {
url: "ajaxcomment.htm",
type: "post",
data: dataString,
dataType: "json",
success: function(data) {
alert(data.getCommentAdded());
},
error: function() {
alert("error");
}
} );
}
Here is my controller
#RequestMapping(value = "ajaxcomment.htm", method = RequestMethod.POST)
public #ResponseBody Comment ajaxcomment(
HttpServletRequest httpServletRequest,
#RequestParam(value = "bookId", required = false) Long bookId,
#RequestParam(value = "parentId", required = false) Long parentId,
#RequestParam(value = "commentId", required = false) Long commentId,
#RequestParam(value = "text", required = true) String text) {
String username = httpServletRequest.getRemoteUser();
User user = userDao.getUserByUsername(username);
Comment comment = new Comment();
// DAO logic
commentDao.addComment(comment);
return comment;
}
Here is my 'Comment' entity:
#Entity #Table(name = "COMMENT") public class Comment implements Serializable {
#Id
#GeneratedValue
#Column(name = "COMMENT_ID", nullable = false)
private Long commentId;
#Column(name = "COMMENT_TEXT", length = 512, nullable = true)
private String commentText;
#Column(name = "COMMENT_ADDED", length = 128, nullable = true)
#Temporal(TemporalType.TIMESTAMP)
private Date commentAdded;
#ManyToOne(cascade = CascadeType.REFRESH, fetch = FetchType.EAGER)
#JoinColumn(name = "BOOK_ID")
private Book book;
#ManyToOne(cascade = CascadeType.REFRESH, fetch = FetchType.EAGER)
#JoinColumn(name = "PARENT_ID")
private Comment parentComment;
#OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER, mappedBy = "parentComment")
#OrderBy("commentAdded")
private Collection<Comment> subcomments;
public void setCommentText(String commentText) {
this.commentText = commentText;
}
public String getCommentText() {
return this.commentText;
}
// other getters and setters are public too
And here is my applicationContext.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:mvc="http://www.springframework.org/schema/mvc"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-2.5.xsd
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">
<mvc:annotation-driven />
<context:component-scan base-package="com.demo"/>
<context:component-scan base-package="com.demo.service"/>
<context:annotation-config />
<bean id="viewResolver" class="org.springframework.web.servlet.view.UrlBasedViewResolver">
<property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
<property name="prefix" value="/WEB-INF/jsp/"/>
<property name="suffix" value=".jsp"/>
</bean>
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"/>
<bean id="jacksonMessageConverter" class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter"/>
<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
<property name="messageConverters">
<list>
<ref bean="jacksonMessageConverter" />
</list>
</property>
</bean>
<bean id="exceptionMessageAdapter"
class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerExceptionResolver">
<property name="messageConverters">
<list>
<!-- Support JSON -->
<ref bean="jacksonMessageConverter" />
</list>
</property>
</bean>

Answer 1

It might be that in your form you are setting values like value="${book.getBookId()}" instead of value="${book.bookId}".
In other words you have to use the expression language by referring to the name of the field in the bean (entity or whatever) rather than trying to use the getter for that field directly.

Answer 2

It works.
I've updated my controller method (handler):
#Autowired private DAOComment commentDao;
#RequestMapping(value = "ajaxcomment.htm", method = RequestMethod.POST)
public #ResponseBody String ajaxcomment(
HttpServletRequest httpServletRequest,
#RequestParam(value = "bookId", required = false) Long bookId,
#RequestParam(value = "parentId", required = false) Long parentId,
#RequestParam(value = "commentId", required = false) Long commentId,
#RequestParam(value = "text", required = true) String text) {
String username = httpServletRequest.getRemoteUser();
User user = userDao.getUserByUsername(username);
Comment comment = new Comment();
// DAO logic
commentDao.addComment(comment);
return "{\"id\":\"" + comment.getCommentId() + "\"," +
"\"username\":\"" + comment.getUser().getUsername() + "\"," +
"\"text\":\"" + comment.getCommentText() + "\"," +
"\"added\":\"" + comment.getFormattedDate() + "\"}";
}
I used \" instead of ' because JSON.parse() doesn't parse string like 'param':'value', "param":"value" only.
Updated script:
<script type="text/javascript">
function ajaxsubmit(buttonId, className){
var formId = document.getElementById(buttonId).parentNode.id;
var dataString = $("#" + formId).serialize();
$.ajax( {
url: "ajaxcomment.htm",
type: "post",
data: dataString,
dataType: "text",
success: function(data) {
var response = JSON.parse(data);
//This's it.
alert(response.id);
},
error: function() {
alert("Error has occured.");
}
} );
}
</script>