Sunday, 25 May 2014

how to find out the foreign keys and their reference table in mysql

Simple query to find the foreign keys and their reference table and fields in Mysql

SELECT * FROM information_schema.TABLE_CONSTRAINTS

WHERE information_schema.TABLE_CONSTRAINTS.CONSTRAINT_TYPE = 'FOREIGN KEY'

AND information_schema.TABLE_CONSTRAINTS.TABLE_SCHEMA = 'myschema'

AND information_schema.TABLE_CONSTRAINTS.TABLE_NAME = 'mytable';

in the place of "my schema" replace with your database name

and in "my table " enter the table for which you want to know the foreign key

2. To find the tables having auto increment fields the following query can be used

SELECT Table_name, IF(AUTO_INCREMENT,1,0) as Auto_increment

FROM INFORMATION_SCHEMA.TABLES

WHERE TABLE_SCHEMA = 'databasename' ;

3. To update tables having foreign key constrains it would be very difficult to drop the foreign keys and

then update the tables for changes in that case we can use the following script for disabling and

enabling foreign key's without dropping the foreign keys

set foreign_key_checks=0;// to disable keys

alter table queries............;//all alter queries should be written here

set foreign_key_checks=1;//to enable keys

this script should be saved as .sql file and that's it you are done....

how to generated auto key in jdbc

JDBC auto Generated Key Sample Program...

/*
* Sairam Rajulapati, Inc. ALL RIGHTS RESERVED.
*/

import java.sql.*;

public class AutoGenKeys {

public static void main(String args[]) {

String url = "jdbc:mySubprotocol:myDataSource";

Connection con = null;
PreparedStatement pstmt;
String insert = "INSERT INTO COFFEES VALUES ('HYPER_BLEND', " +
"101, 10.99, 0, 0)";
String update = "UPDATE COFFEES SET PRICE = ? WHERE KEY = ?";

try {

Class.forName("myDriver.ClassName");

} catch(java.lang.ClassNotFoundException e) {
   System.err.print("ClassNotFoundException: ");
   System.err.println(e.getMessage());
}

try {

   con = DriverManager.getConnection(url,
"myLogin", "myPassword");

pstmt = con.prepareStatement(insert,
Statement.RETURN_GENERATED_KEYS);

pstmt.executeUpdate();
ResultSet keys = pstmt.getGeneratedKeys();

int count = 0;

keys.next();
int key = keys.getInt(1);

pstmt = con.prepareStatement(update);
pstmt.setFloat(1, 11.99f);
pstmt.setInt(2, key);
pstmt.executeUpdate();

keys.close();
pstmt.close();
      con.close();

} catch (SQLException e) {
   e.printStackTrace();
}

}

}

how to implement the intercepters in struts2

Sample Example

package com.googleforjava.interceptor;

import java.util.Iterator;
import java.util.Map;

import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.interceptor.Interceptor;

public class TestActionInterceptor implements Interceptor {

/**
*
*/
private static final long serialVersionUID = 1L;

public void destroy() {
System.out.println("CustomInterceptor destroy() is called...");

}

public void init() {
System.out.println("CustomInterceptor init() is called...");

}

public String intercept(ActionInvocation actionInvocation) throws Exception {
System.out.println("CustomInterceptor, before invocation.invoke()...");

Map params = actionInvocation.getInvocationContext().getParameters();
// Getting all request parameters from jsp page on which you have called any
// action
System.out.println(params.size());
Iterator itr = params.entrySet().iterator();
while(itr.hasNext()) {
   Object element = itr.next();
   System.out.print(element + " ");
   Map.Entry pairs = (Map.Entry)itr.next();
System.out.println(pairs.getKey() + " = " + pairs.getValue());
}
System.out.println("Stack :"+actionInvocation.getStack().size());
System.out.println("Stack :"+actionInvocation.getStack().VALUE_STACK);
params = actionInvocation.getStack().getContext();
itr = params.entrySet().iterator();
while(itr.hasNext()) {
   Object element = itr.next();
   System.out.print(" --> "+element + " ");
   Map.Entry pairs = (Map.Entry)itr.next();
System.out.println(pairs.getKey() + " = " + pairs.getValue());
}

System.out.println(" Action Name : "+actionInvocation.getAction().toString());
String result = actionInvocation.invoke();
System.out.println(" Result : "+ result);

System.out.println("CustomInterceptor, after invocation.invoke()...");

return result;
}

}

  Struts2 Interceptor Read Parameter in interceptor class

in struts.xml file
in one common package.

<interceptors>
<interceptor name="crunchPrepInterceptor" class="com.googleforjava.thinksharp.interceptorsPrep.GatePass" />
<interceptor-stack name="thinksharpPrepStack">
<interceptor-ref name="thinksharpPrepInterceptor"/>
<interceptor-ref name="defaultStack" />
</interceptor-stack>
</interceptors>
<default-interceptor-ref name="thinksharpPrepStack"></default-interceptor-ref>

in interceptor class:

 HttpServletResponse response = (HttpServletResponse) invocation.getInvocationContext().get(StrutsStatics.HTTP_RESPONSE);

Map sessionMap = actionInvocation.getInvocationContext().getSession();


  String className = actionInvocation.getAction().getClass().getName();

  

  

   System.out.println("Stack :"+actionInvocation.getStack().size());

   System.out.println("Stack :"+actionInvocation.getStack().VALUE_STACK);

   HttpServletRequest request = ServletActionContext.getRequest();

  System.out.println(" Action Name  : "+actionInvocation.getAction().toString());

  

  LoginUserBO loginUserBO=(LoginUserBO) sessionMap.get("user");

  System.out.println("\n\n\n\n B4 Invocation Interceptor \n Class Name is: "+className);

  if(loginUserBO==null){

   System.out.println("\n\n User Object is null ");

  }else{

   userDetails(loginUserBO);

  }

  

  String result=actionInvocation.invoke();

  sessionMap = actionInvocation.getInvocationContext().getSession();

   loginUserBO=(LoginUserBO) sessionMap.get("user");

  System.out.println("\n\n\n After Invocation Interceptor Result is: "+result);

  if(loginUserBO==null){

   System.out.println("\n\n User Object is null ");

  }else{

   userDetails(loginUserBO);

  }

  return result;

 }

  private void userDetails(LoginUserBO loginUserBO)

  {

   System.out.println("\n\n User Name is: "+loginUserBO.getFirst_name()+" User Role Id is :"+loginUserBO.getRole_id());

  }

what is web.xml

WEB.XML REFERENCE GUIDE FOR TOMCAT

Introduction

The web.xml Deployment Descriptor file describes how to deploy a web application in a servlet container such asTomcat.

This file is required for every application you deploy on Tomcat. You will find one in the jsp-examples, servlet-examples and ROOT

applications

provided on a new Tomcat website, and every web application example you download, including inside WAR files.

The location of the file is always the same: application root/WEB-INF/web.xml

At minimum, the file needs to contain an XML descriptor and an opening and closing <web-app> tag.

Here is a minimal XSD-style example for Tomcat 6.0. For other versions (7.0, 5.5, 5.0 etc..) and to compare XSD and DTD declarations, see web.xml DTD and XSD.

<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
     version="2.5">

</web-app>

Inside the <web-app> tag, a number of other elements can be added. These are detailed below.

Detailed Reference - click a tag for more information

<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" version="2.4">     <display-name>Example App</display-name> <description>An example application which is used to play with some of the features of Tomcat</description>  <distributable />  <session-config> <session-timeout>120</session-timeout> </session-config>           <jsp-config> <jsp-property-group> <url-pattern>*.jsp</url-pattern> <include-prelude>/WEB-INF/jspf/prelude1.jspf</include-prelude> <include-coda>/WEB-INF/jspf/coda1.jspf</include-coda> </jsp-property-group> </jsp-config>    <context-param> <description>Enable debugging for the application</description> <param-name>debug</param-name> <param-value>true</param-value> </context-param> <context-param> <description>The email address of the administrator, used to send error reports.</description> <param-name>webmaster</param-name> <param-value>address@somedomain.com</param-value> </context-param>    <env-entry> <env-entry-name>webmasterName</env-entry-name> <env-entry-value>Ms. W. Master</env-entry-value> <env-entry-type>java.lang.String</env-entry-type> </env-entry> <env-entry> <env-entry-name>cms/defaultUserSettings/recordsPerPage</env-entry-name> <env-entry-value>30</env-entry-value> <env-entry-type>java.lang.Integer</env-entry-type> </env-entry> <env-entry> <env-entry-name>cms/enableXMLExport</env-entry-name> <env-entry-value>false</env-entry-value> <env-entry-type>java.lang.Boolean</env-entry-type> </env-entry> <env-entry> <env-entry-name>cms/enableEmailNotifications</env-entry-name> <env-entry-value>true</env-entry-value> <env-entry-type>java.lang.Boolean</env-entry-type> </env-entry>     <servlet> <servlet-name>Simple</servlet-name> <servlet-class>SimpleServlet</servlet-class> <description>This is a simple Hello World servlet</description> </servlet> <servlet-mapping> <servlet-name>Simple</servlet-name> <url-pattern>/servlet/SimpleServlet</url-pattern> </servlet-mapping>  <servlet>  <servlet-name>cms</servlet-name> <servlet-class>com.metawerx.servlets.ContentManagementSystem</servlet-class> <description>This servlet handles requests for the CMS (it is a controller in an MVC architecture)</description>  <init-param> <param-name>debug</param-name> <param-value>true</param-value> </init-param> <init-param> <param-name>detail</param-name> <param-value>2</param-value> </init-param>  <load-on-startup>5</load-on-startup>  </servlet>  <servlet-mapping>  <servlet-name>cms</servlet-name> <url-pattern>*.cms</url-pattern> </servlet-mapping>   <servlet> <servlet-name>rewriter</servlet-name> <servlet-class>com.metawerx.servlets.URLRewriter</servlet-class> </servlet>  <servlet-mapping>  <servlet-name>rewriter</servlet-name> <url-pattern>/content/*</url-pattern> </servlet-mapping> <servlet-mapping>  <servlet-name>rewriter</servlet-name> <url-pattern>/admin/RewriterStatistics</url-pattern> </servlet-mapping>   <servlet> <servlet-name>pathjsp</servlet-name> <jsp-file>pathfinder.jsp</jsp-file> </servlet>  <servlet-mapping>  <servlet-name>pathjsp</servlet-name> <url-pattern>/shop/item/*</url-pattern> </servlet-mapping>     <filter> <filter-name>Set Character Encoding</filter-name> <filter-class>filters.SetCharacterEncodingFilter</filter-class> <init-param> <param-name>encoding</param-name> <param-value>EUC_JP</param-value> </init-param> </filter> <filter-mapping> <filter-name>Set Character Encoding</filter-name> <url-pattern>/*</url-pattern> </filter-mapping>  <filter> <filter-name>Request Dumper Filter</filter-name> <filter-class>filters.RequestDumperFilter</filter-class> </filter> <filter-mapping> <filter-name>Request Dumper Filter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping>     <listener> <listener-class>com.metawerx.listener.ContextListener</listener-class> </listener> <listener> <listener-class>com.metawerx.listener.SessionListener</listener-class> </listener>     <security-role> <role-name>admin</role-name> </security-role> <security-role> <role-name>cms_editors</role-name> </security-role>  <security-constraint> <display-name>Security constraint for the /private folder</display-name> <web-resource-collection> <web-resource-name>Protected Area</web-resource-name> <url-pattern>/private/*</url-pattern>    </web-resource-collection> <auth-constraint>  <role-name>admin</role-name> <role-name>cms_editors</role-name> </auth-constraint> </security-constraint>     <login-config> <auth-method>BASIC</auth-method> <realm-name>Editor Login</realm-name> </login-config>  <security-constraint> <web-resource-collection> <web-resource-name>Entire Application</web-resource-name> <url-pattern>/*</url-pattern> </web-resource-collection> <user-data-constraint> <transport-guarantee>CONFIDENTIAL</transport-guarantee> </user-data-constraint> </security-constraint>     <error-page> <error-code>404</error-code> <location>/error404.jsp</location> </error-page>  <error-page> <exception-type>java.lang.Throwable</exception-type> <location>/errorThrowable.jsp</location> </error-page>     <mime-mapping> <extension>xls</extension> <mime-type>application/vnd.ms-excel</mime-type> </mime-mapping>     <locale-encoding-mapping-list> <locale-encoding-mapping> <locale>ja</locale> <encoding>Shift_JIS</encoding> </locale-encoding-mapping> </locale-encoding-mapping-list>        <welcome-file-list>  <welcome-file>index.swf</welcome-file> <welcome-file>splash.jsp</welcome-file> <welcome-file>index.html</welcome-file> <welcome-file>index.htm</welcome-file> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>