Hi, welcome to this series of Jasper's of reports. In this video, we are going to see the basics of variables in Jasper's of design studio. The agenda for this session is, firstly, I will walk you through water variables and their usage. Then, we take a look at the properties of the variable and finally, we will see an example on how to create a variable and use it in a report. Let's get started. What are variables and their usage? A variable in Jasper report is a container to store a value or a result based on the daughter retrieved from the database. Variables are generally used in complex calculation or in calculating the other variables. All is a reporting object in the studio and we represent it with the owner, we hear. Now, let us take a look at the properties of a variable. Every variable that we create in a report will get a name, classning, calculation, expression, initial value, expression, increment type, increment of factory class name, reset type. We can consider name, class name, calculation, expression, initial value, expression or the base properties of a variable. The available functions for calculation are some average, count, lowest and highest. There are several other functions available for the calculation. Now, let's have a look at the advanced properties of a variable. We can consider increment type and reset type or the advanced properties of a variable. Let us briefly look at what is increment type and what is reset type, increment type. Increment type is an advanced attribute of a variable. It is basically used to change the time on which the calculation function is used. The passable values for the increment type are none, repo, page and column. We also have additional increment type that is group. Increment type, increment type, calculation is based on the expression. That means when a calculation function is defined, the expression is passed on to the function and the function will do the calculation for the variable. The default behavior is to do the calculation at every record level. We use increment types on the functions. If we select increment type as none, the calculation function is called for each record that we retrieve from the database. If we select the increment type as R.P. The calculation function is called at the end of the R.P. If we select the increment type as page, the calculation of function is called at the end of the each page. Similarly if we select increment type as column, the calculation function is called at the end of the each column. And if we select the additional increment type, which is group, then the calculation function is called at the start of the every occurrence of the group's specified. It is visible in the dropdown if the report is having at least one group created. Now let's briefly look at what is reset type. Reset type is another advanced property of a variable. It is basically used to define when to reset the value of a variable to its initial value. We generally use reset type on the group by summations. The possible values for the reset type are none, repo, page, column and group by. If we select reset type as none, the variable is the variable will never get be in Slider. That means the initial value expression will be ignored. If we select reset type as report, the variable, the variable is in Slizer at this start of the report creation. And if you select reset type as page, the variable is in Slizer at the each page. If we select reset type as column, the variable will, the variable is in Slizer on each new column. If we select reset type as group, the variable is initialized at the start of every occurrence of the report. Again, it is visible. That means the group is visible in the dropdown for the reset type. If the report contains at least one group. Now let's take now it is time to create a now it is time to create a variable and use that variable in a report. Let us take the scenario of a product detail report. Now it's time to create a report in the studio. Create a blank report from file new Jasper report. Select blank A4 template for the from the report templates result. Click on next button and let's give a name for this report. I am taking variables and some of the column product detail report as the report name here. Let's save this report under Jasper reports 2021 folder and I already have a folder sub folder called as reports. I am going to save this report in reports folder. Then click on next from the data adapter dropdown. Select the footmap database. Let's keep providing query for now. So click on either next or finish button to have the report design we already click OK click finish. Now in the PG admin SQL editor query the product table with product ID, product name, grass weight and net weight fields. Let's quickly run this query to with the result set in the bottom. So we have now a total of 11 records and we are going to find the total total for the net weight column in the report by creating a variable. So let's copy this query and paste it in the SQL editor of the studio. We need to ensure that the footmap database is selected from the top left dropdown and the language type must be SQL. Now click on read field button and in the bottom we can see field name and class types are retrieved from the database. Now from the bottom you know just click on data preview and then click on refresh preview data so that we can see the sample records retrieved from the database. Click OK then save the report. Now from the hierarchical view of the outline select fields, expand it and select all the fields from the fields node and drag it on to them and drag it on to the detail band. Let's quickly format this report to not to have any empty spaces and and also remove the unnecessary bands from the report. We need to have the column photo where we are going to place the variable that we are going to create. So let's skip the column photo available in the design space. Now let's add a title to the report. Try to text from the palette then give the same name that we use it for saving the report. That is variable sign some of the column from a for product detail report. So title is given. Click finish then adjust the width of the text fill and let's remove the empty space from the title band. We don't require this page header band here so let's remove this one. Quickly adjust the heights of the text fill horizontally and vertically middle. Now we have the report ready which will which will look like a grid grid formats. Let's give border to all of them. Properties from border and select all borders for this one. Let's preview this report and run it. Click on preview button from the bottom tabs then click on run button. Now we have the product detail report ready with us. Now we are going to create a variable to find the total of the net weight field. So we reach it to the core part of creating a variable in the report. For that. From the hierarchical outline view select variables right click on it. Then click on create variable. By default variable underscore one is created and if you look at the properties of this variable. We can have name value class name. Then the calculation by default it is no calculation function. Let's let's change this calculation from no calculation function to some. And let's also replace this variable underscore one to a meaningful name something like variable. Total net weight. That was a suggestion because I already have created a variable in the in some other report. So let's take let's name it as variable total net weight. And we need to provide the expression for this variable. We are going to find the total for the net weight column. So let's give the expression as net weight. Open the expression editor and then select net weight field. Click on finish. By default when we create a variable the increment type is none and the reset type is report. Let's do not change these values for now for this demonstration. Now select the variable total net weight that we just created from the variable note and drag it onto the column footer just beneath through the net weight field. So we are done here we just created a variable and we pulled that variable onto the column footer band. Let's quickly run this report and see what it offers. Before running let's quickly format this one. Select same click on preview and run the report. Looks like we have some error generated. In the next section we have the error. Jr field expression error evaluating expression for source text. Let's go back to the design view and see what the error was. So here the error is related to the type of the variable by default when we create a variable it takes the string type. Let's change these to flow. Let's match let's match the type of this variable to the type of what on what field we are creating the variable. So in this case the type of net weight field is flow. So we need to match the same type to the variable. Select the report and run it again. Click preview. So now we have the product detail before displayed and if we scroll down to the bottom we can see the total for the net weight field is displayed here. So this is how we can create a variable for a report and we can make use of the report in the column footer band to calculate the summation of the summation of a particular column. I would like to tell you that there is an easiest way to create a variable. For example if we want to calculate the total for the gross weight fields from the field section just select the particular field which is gross weight in this in this case and drag it on to the column footer just beneath to the gross weight column. So as we drag that field it open it open submit text fill wizard which contains the possible functions that we can apply for apply on the field. So let's take some here and click on finish. As we drop as we drop this function here on to the column footer band the report will generate a variable with the field name in the variable section. Let's have a look at the properties of this one. So the name is given as cross weight one then the value class name is taken as float by default then we have selected some while dragging and dropping the gross weight field and the expression is taken as dollar f gross weight and by default increment type is taken as reset type as column. So this is another alternative to create a report. If we closely look at the properties of the created variable and the properties of generated variable we can we can understand that the reset type is column for the generated one and the reset type for the created one by default is report. Let's do not worry about how these how these are appearing for the created and the generated fields. As we get command on the variables we can easily understand how effectively we can make use of these variables. So this brings us to the end of this session. I hope you are a bit clearer on what we saw today. Before we wrap up let's quickly recap what we have seen so far. So we have seen firstly I walk you through water variables and their usage. Then we took a look at the properties of variable and finally we have seen how we can create how we can create and use a variable in a report. So that's all for this session. I hope you liked it. Let's get straight to note for more updates on the upcoming videos. Thank you.