Andrea Girardi - It's my blog!

Tag: java (page 1 of 3)

How do I fix a 65535 bytes limit Stacktrace?

It is possible that after an upgrade you may encounter this error on some of the more complex pages and root cause provided by tomcat console is :

Unable to compile class for JSP
The code of method _jspService(HttpServletRequest, HttpServletResponse) is exceeding the 65535 bytes limit

To solve the issue you need to locate the file [Tomcat_Home]/conf/web.xml and search the file for ‘JspServlet’. This should return an xml node of containing some values. You will need to add an additional the same as the below.

<init-param>
     <param-name>mappedfile</param-name>
     <param-value>false</param-value>
</init-param>

The resulting block of the web.xml file, once you have inserted the above, should look like the code below.

<servlet>
	<servlet-name>jsp</servlet-name>
	<servlet-class>org.apache.jasper.servlet.JspServlet</servlet-class>
	<init-param>
	    <param-name>fork</param-name>
	    <param-value>false</param-value>
	</init-param>
	<init-param>
	    <param-name>xpoweredBy</param-name>
	    <param-value>false</param-value>
	</init-param>
	<init-param>
	     <param-name>mappedfile</param-name>
	     <param-value>false</param-value>
	</init-param>         
	<load-on-startup>3</load-on-startup>
</servlet>

Save the file and restart the Tomcat service.

MappingJacksonHttpMessageConverter not found

I was trying to run a java batch that call an application context without success (it’s a java app that calls a Camel spring context). This is what I get during the startup:

ERROR ApplicationProperties @ addApplicationProperty [28] org.springframework.beans.factory.BeanDefinitionStoreException: Unexpected exception parsing XML document from file [/MessageRouting/src/test/resources/META-INF/spring/LOCALHOST-db-context.xml]; nested exception is java.lang.NoClassDefFoundError: org/springframework/http/converter/json/MappingJacksonHttpMessageConverter
Fatal error! java.lang.RuntimeException: Error loading ClassPathXmlApplicationContext file - src/test/resources/META-INF/spring/LOCALHOST-db-context.xml

I’m using spring 4.2.3 (updated yesterday, probably the reason for which it doesn’t work. It was 4.0.9). I know that MappingJacksonHttpMessageConverter has been replaced by MappingJackson2HttpMessageConverter but, how can I tell to spring to use the new version???

I followed some suggestion and I added this to my pom.xml:

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-core</artifactId>
    <version>2.6.3</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.6.3</version>
</dependency>   
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-annotations</artifactId>
    <version>2.6.3</version>
</dependency>

But this didn’t fix so, I finally resolved the issue adding this dependency to my pom.xml:

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-webmvc</artifactId>
    <version>${org.springframework-version}</version>
</dependency>

Which log4j configuration are you using?

Sometimes log4j is not working properly and you need to verify where it is actually writing the log entries. This can be easily verified turning on the log4j.debug:

-Dlog4j.debug

It will print to System.out lots of helpful information about which file it used to initialize itself, which loggers / appenders got configured and how etc.

Parse an unknown JSON with Jquery

Sometime it happens to receive a JSON string than need to be visualized without knowing the structure. Suppose we have an HTML table:

<tbody id="reportTable">					
</tbody>

To populate this table with jQuery it’s possible to use this simple code:

var rows = ${reportRows};
var html = $.each(rows, function(key, value){
 
	$("#reportTable").append("<tr>");
 
	$.each(value, function (key, data) {
		$("#reportTable").append("<td>" + data + "</td>");
	});
 
	$("#reportTable").append("</tr>");
 
});

${reportRows} comes from a Spring MVC Controller and it’s a Java string generates using Jackson (or Gson) in this way:

ColumnMapRowMapper rowMapper = new ColumnMapRowMapper();
List<Map<String, Object>> reportDataList =  getJdbcTemplate().query(sqlComplete, rowMapper);
 
ObjectWriter ow = new ObjectMapper().writer().withDefaultPrettyPrinter();
String json = ow.writeValueAsString(reportDataList);

So, we have a query that return a not know number of column (suppose your code dynamically generate the query), we translate the results in JSON and we use jQuery to render the results.

Dynamic for with Spring MVC using a HashMap

Sometime you need to dynamically generate a form without knowing how many fields it will be required (i.e. when your form is driven by a configuration or by some properties). The problem is to draw the form and, return the values to the Controller, and recognize the couples Field name / Field value after the submit..

You can easily get solve this problem just adding HashMap which will hold the key-value pair data to the DataModel.

Supposing your configuration says: you have to draw two fields and these are the name, you UI will be something like*:

<c:forEach items="${newRequest.fields}" var="field">
	<f:input type="text" path="rawFields['${field.field_id}']" class="form-control validate[groupRequired[mandatoryField]]" /> (R)
</c:forEach>

When you submit the form, the values and the key for the dynamic fields will be filled.

* newRequest is the DataModel you are passing and fields is the list of Fields that user will fill with data, like that:

public class Request {
 
	/** Request type */
	private int templateRequest;
 
	// ***** Input field ***** 
	List<RequestField> fields = new ArrayList<RequestField>();
 
	private HashMap<String, Object> rawFields = new HashMap<String, Object>();
 
	[Setters and getters]
 
}

Results pagination with MongoDB and Java

To implement the MongoDB results pagination in Java, there are few parameters that need to be collected:

1) the order of results (ascending / descending)
2) the field used to order the results
3) the number of element and the page selected
4) the field and the value used to filter the results

As well as the results of query, the method needs to return the total number of elements. All returned elements will be saved in a HashMap.

HashMap&lt;String, Object&gt; resultMap = new HashMap&lt;String, Object&gt;();
 
Direction direction = Sort.DEFAULT_DIRECTION;
if (sortDirection &gt; 0) {
	direction = Sort.Direction.ASC;
} else { 
	direction = Sort.Direction.DESC;
}
 
List

If a pagination is required, skip and limit are used

if (pageSize &gt; 0) {
	query.skip((pageNum - 1 ) * pageSize);
	query.limit(pageSize);
}
 
if ( sortField != null &amp;&amp; !sortField.equals("") ) {				
	query.with(new Sort(direction, sortField));
}
 
results = mongoTemplate.find(query, Object.class);

If a pagination is required, queryCounter (basically a version of query without pagination an limit) is used to calculate the total number of results. Of course, if pagination is not required, is possible to use directly the size of results.

if ( pageSize &gt; 0 ) {
	resultMap.put("RESULT_SIZE", (int) mongoTemplate.count(queryCounter, Object.class));
} else {
	// If pagination is not required, the query is not re-executed
	resultMap.put("RESULT_SIZE", results.size());
}

mongoTemplate is a spring bean defined in this way on context configuration:

<bean id="mongoTemplate" class="org.springframework.data.mongodb.core.MongoTemplate"  c:mongo-ref="mongo" c:databaseName="${mongo.db.name}">
	<property name="writeConcern" value="SAFE" />
</bean>

MongoDB query with logical and condition in Java

Suppose you need to apply some filters to your MongoDB query, for example to extract some _ids that match a regex condition. This is the way to do that:

Query query;
query.addCriteria(Criteria.where("_id").in(IDs).and(query_field).regex(".*" + query_value + ".*", "i"));

In this example I used the Query (see here) and Criteria (see here) classes

And, this is the query you can use in mongoDB (Robomongo* or command line):

Query: { 
	"_id" : { "$in" : [ "ID1" , "ID2" , "ID3" ]} , 
	"detail.medicationBrandName" : { "$regex" : ".*x.*" , "$options" : "i"}}, 
	Fields: null, Sort: { "medicationGenericName" : -1}
}

*Robomongo: is a shell-centric cross-platform open source MongoDB management tool (i.e. Admin GUI). Robomongo embeds the same JavaScript engine that powers MongoDB’s mongo shell. You can download it here.

dataSource: The name of the property, following JavaBean naming conventions.

Suppose you defined TemplateDao Spring bean in this way:

<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">	
	<property name="driverClassName"><value>com.mysql.jdbc.Driver</value></property>	
	<property name="url"><value>jdbc:mysql://${mysql.hostname}:${mysql.port}/${mysql.db}</value></property>
	<property name="username"><value>${mysql.user}</value></property>
	<property name="password"><value>${mysql.password}</value></property>
</bean>	
 
<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
	<property name="dataSource" ref="dataSource"/>
</bean> 
 
<bean id="TemplateRequestDao" class="com.afm.admin.dao.mysql.TemplateDaoMySql">
	<property name="dataSource" ref="dataSource" />
</bean>

and you get this error message: The name of the property, following JavaBean naming conventions. The reason is probably you forgot to extend your implementation class:

public class TemplateDaoMySql extends JdbcDaoSupport implements TemplateDao {
 
	@Override
	public List<TemplateRequest> getTemplateRequest(UserProfile userProfile) {
		// TODO Auto-generated method stub
		return null;
	}
 
}

Time lost to fix this issue: more or less 1 hour. Image the how many I was frustrated when I discovered what was the problem.

Velocity generates NullPointerException while evaluating template

While evaluating template with Velocity I am affecting a null point exception but happened only on production environment because it seems that the application is trying to write to tomcat/bin the velocity.log file but it failed due to the permission. I tried to add velocity.property file:

# Fri Dec  6 10:14:26 EST 2013 - Mandatory to prevent Velocity null point exception
runtime.log.logsystem.class=org.apache.velocity.runtime.log.NullLogSystem

but, after every startup I get the same error and, to fix that, it seems to be mandatory to remove the workdir tomcat folder. It’s not acceptable so, I tried to add this row before init the velocity:

Velocity.setProperty("runtime.log.logsystem.class", "org.apache.velocity.runtime.log.NullLogSystem");

Of course, my next step is to migrate to Freemarker because Velocity isn’t really under active development any more.

Cannot nest ‘PRJ/src/main/resource’ inside ‘PRJ/src’

I created a new Web application using Eclipse and, after Enabling Maven, I get this error updating the project:

Cannot nest 'PRJ/src/main/resource' inside 'PRJ/src'. To enable the nesting exclude 'main/' from 'PRJ/src'

Basically I removed the folder /src and create folder /src/main/java, /src/main/resources etc and this fight with the sourceDirectory tag in Build section of maven pom. To fix that, just remove this row and update the project:

<sourceDirectory>src/</sourceDirectory>
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