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Java Articles
Page 419 of 450
How can I create custom tag in JSP which can accept attribute from parent jsp page?
You can use various attributes along with your custom tags. To accept an attribute value, a custom tag class needs to implement the setter methods, identical to the JavaBean setter methods as shown below −package com.tutorialspoint; import javax.servlet.jsp.tagext.*; import javax.servlet.jsp.*; import java.io.*; public class HelloTag extends SimpleTagSupport { private String message; public void setMessage(String msg) { this.message = msg; } StringWriter sw = new StringWriter(); public void doTag() throws JspException, IOException { if (message != null) { /* Use message from attribute ...
Read MoreWhat are the standard attributes that should be passed to a custom tag in a JSP page?
Consider including the following properties for an attribute −S.No.Property & Purpose1nameThe name element defines the name of an attribute. Each attribute name must be unique for a particular tag.2requiredThis specifies if this attribute is required or is an optional one. It would be false for optional.3rtexprvalueDeclares if a runtime expression value for a tag attribute is valid4typeDefines the Java class-type of this attribute. By default, it is assumed as String5descriptionInformational description can be provided.6fragmentDeclares if this attribute value should be treated as a JspFragment.Following is the example to specify properties related to an attribute −..... ...
Read MoreHow to pass check boxes data using JSP?
Checkboxes are used when more than one option is required to be selected.Following is an example HTML code, CheckBox.htm, for a form with two checkboxes. Maths Physics Chemistry The above code will generate the following result − Maths Physics Chemistry Following is main.jsp JSP program to handle the input given by the web browser for the checkbox button. Reading Checkbox Data Reading Checkbox Data Maths Flag: Physics Flag: Chemistry Flag: The above program will generate the following result −Reading Checkbox DataMaths Flag :: onPhysics Flag:: nullChemistry Flag:: on
Read MoreHow to use a filter in JSP?
Following example shows how to print the client's IP address and the current date time, each time it would access any JSP file. This example will give you a basic understanding of the JSP Filter, but you can write more sophisticated filter applications using the same concept −// Import required java libraries import java.io.*; import javax.servlet.*; import javax.servlet.http.*; import java.util.*; // Implements Filter class public class LogFilter implements Filter { public void init(FilterConfig config) throws ServletException { // Get init parameter String testParam = config.getInitParameter("test-param"); //Print the init parameter ...
Read MoreHow do you define multiple filters in JSP?
Your web application may define several different filters with a specific purpose. Consider, you define two filters AuthenFilter and LogFilter. Rest of the process will remain as explained above except you need to create a different mapping as mentioned below − LogFilter LogFilter test-param Initialization Paramter AuthenFilter AuthenFilter test-param Initialization Paramter LogFilter /* AuthenFilter /* Filters Application OrderThe order of filter-mapping elements ...
Read MoreWhat is the difference between execute(), executeQuery() and executeUpdate() methods in JDBC?
Once you have created the statement object you can execute it using one of the execute methods of the Statement interface namely, execute(), executeUpdate() and, executeQuery().The execute() method: This method is used to execute SQL DDL statements, it returns a boolean value specifying weather the ResultSet object can be retrieved.Exampleimport java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.sql.Statement; public class Example { public static void main(String args[]) throws SQLException { //Registering the Driver DriverManager.registerDriver(new com.mysql.jdbc.Driver()); //Getting the connection String mysqlUrl = "jdbc:mysql://localhost/sampleDB"; Connection con = ...
Read MoreIs it mandatory to close JDBC connections?
At the end of your JDBC program, it is required explicitly to close all the connections to the database to end each database session. However, if you forget, Java's garbage collector will close the connection when it cleans up stale objects.Relying on the garbage collection, especially in database programming, is a very poor programming practice. You should make a habit of always closing the connection with the close() method associated with connection object.To ensure that a connection is closed, you could provide a 'finally' block in your code. A finally block always executes, regardless of an exception occurs or not.To ...
Read MoreWhy are Prepared Statements in JDBC faster than Statements? Explain?
While executing statements using Statement object, especially insert statements, each time a query is executed the whole statement is compiled and executed again and again where, the only difference among these statements is the values of the statements.Whereas, prepared statement is a precompiled statement i.e. the query is compiled and stored in the database, using place holders (?) instead of values and values to these place holders are supplied later.Thus, avoiding unnecessary compilation and execution of the statement again and again.ExampleSuppose, we have a table named Dataset in the database with the columns mobile_brand and unit_sale, if we want to ...
Read MoreWhat are the advantages and limitations of JDBC PreparedStatement?
Following are the advantages of the prepared statement:By avoiding multiple compilation and execution of statements, prepared statements perform faster.Using prepared statements, we can insert values to advanced datatypes such as BLOB, CLOB, OBJECT easily with the help of the setter methods provided by the PreparedStatement interface.By providing setter method to set values prepared statement avoids the use of quotes and other special characters with in the query, and thereby it escapes the SQL injection attacksFollowing are the limitations of prepared statements:Since a PreparedStatement object represents only one SQL statement at a time, we can execute only one statement by one ...
Read MoreCan we call functions using Callable Statements? Explain with an example in JDBC?
Like procedures, you can also create function in a database and store them.SyntaxFollowing is the syntax of creating a function in a(MySQL) database:CREATE FUNCTION Function_Name(input_arguments) RETURNS output_parameter BEGIN declare variables; statements . . . . . . . . . . return data_type; ENDExampleSuppose we have a table named Emp in the database with the following content:+--------+------------+----------------+ | Name | DOB | Location | +--------+------------+----------------+ | Amit | 1970-01-08 | Hyderabad | | Sumith | 1970-01-08 | Vishakhapatnam | | Sudha | 1970-01-05 | Vijayawada ...
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