NoClassDefFoundError JsonAutoDetect while parsing JSON object

I am developing a webapp using Amazon's cloud services and I need to make use of JSON objects. How my project is set up is, I have an HTML form where the user will fill in their information and submit. Once submitted the data will be placed into an online database and a confirmation email is sent to them. Before I can submit the data to the data base I need to place all of it into a JSON object. My servlet, done in Java, looks like this:

public class FormHandling extends HttpServlet {
    //doGet function
    public void doGet (HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
        // In this part of the code I take in the user data and build an HTML
        // page and return it to the user

        // Create String Mapping for User Data object
        Map<String,Object> userData = new HashMap<String,Object>();

        // Map the names into one struct. In the code below we are creating 
        // values for the nameStruct from the information the user has
        // submitted on the form.
        Map<String,String> nameStruct = new HashMap<String,String>();
        nameStruct.put("fName", request.getParameter("fname"));
        nameStruct.put("lName", request.getParameter("lname"));
        nameStruct.put("mInit", request.getParameter("minit"));

        // Map the three email's together (providing there are 3).
        // This is the same logic as the names.
        Map<String,String> emailStruct = new HashMap<String,String>();
        emailStruct.put("email", request.getParameter("email1"));
        emailStruct.put("email", request.getParameter("email2"));
        emailStruct.put("email", request.getParameter("email3"));

        // Put Name Hash Value Pair inside User Data Object
        userData.put("name", nameStruct);
        userData.put("emails", emailStruct);
        userData.put("age", 22);

        // Create the Json data from the userData
        createJson(userData);

        // Close writer
        out.close();
    }

    public File createJson(Map<String,Object> userData) 
        throws JsonGenerationException, JsonMappingException, IOException {
        File user = new File("user.json");

        // Create mapper object
        ObjectMapper mapper = new ObjectMapper();

        // Add the userData information to the json file
        mapper.writeValue(user, userData);
        return user;
    }
}

When I submit the form using this code I get the following error message:

java.lang.NoClassDefFoundError: com/fasterxml/jackson/annotation/JsonAutoDetect com.fasterxml.jackson.databind.introspect.VisibilityChecker$Std.(VisibilityChecker.java:169) com.fasterxml.jackson.databind.ObjectMapper.(ObjectMapper.java:197) edu.tcnj.FormHandling.createJson(FormHandling.java:115) edu.tcnj.FormHandling.doGet(FormHandling.java:104) edu.tcnj.FormHandling.doPost(FormHandling.java:131) javax.servlet.http.HttpServlet.service(HttpServlet.java:641) javax.servlet.http.HttpServlet.service(HttpServlet.java:722)

Now I know that error means that it isn't finding the Jackson databind library. I am developing in Eclipse and I know the build path messes up from time to time so I also placed the libraries in the WebContent\WEB-INF\lib folder. This has solved issues I've had before. However, this does not seem to solve my problem this time around. I have even opened the jar files to physically check that the library and class needed are there, and they are. I've tried searching all over and looking into different ways to include the library but nothing seems to work.

i_am_jorf

For those who come here in the future, the answer is:

If you've only copied jackson core and jackson databind, you need jackson annotations to use the ObjectMapper.

For example, make sure you have something like this:

[16:32:01]:/android-project/libs     master]$ ls -lAF
total 2112
-rw-r--r--@ 1 jeffamaphone  staff   33525 Jun 18 16:06 jackson-annotations-2.0.2.jar
-rw-r--r--@ 1 jeffamaphone  staff  193693 Jun  7 16:42 jackson-core-2.0.2.jar
-rw-r--r--@ 1 jeffamaphone  staff  847121 Jun 18 15:22 jackson-databind-2.0.2.jar

To expand on @jeffamaphone's excellent answer, for maven users

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-core</artifactId>
    <version>2.7.3</version>
</dependency>

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.7.3</version>
</dependency>

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-annotations</artifactId>
    <version>2.7.3</version>
</dependency>

Or the following gradle configuration:

compile 'com.fasterxml.jackson.core:jackson-core:2.2.2'
compile 'com.fasterxml.jackson.core:jackson-databind:2.2.2'
compile 'com.fasterxml.jackson.core:jackson-annotations:2.2.2'

If you use maven and have all libraries in place as in my case a simple mvn clean and mvn install fixed problem.

If you are/were using tomcat while developing in eclipse and got this error(maybe because you pressed republish/clean),

a right click on the project->Maven->Update Project...

solved this issue for me.

In addition, i did include also the dependencies from Johan Sjöberg

来源：https://stackoverflow.com/questions/10094300/noclassdeffounderror-jsonautodetect-while-parsing-json-object

标签

java