Develop Java UDFs with MaxCompute Studio - MaxCompute - Alibaba Cloud Documentation Center

IntelliJ IDEA is an integrated development environment (IDE) for Java used to quickly develop Java programs. This topic shows you how to use MaxCompute Studio, a plug-in for IntelliJ IDEA, to develop a Java user-defined function (UDF) that converts uppercase letters to lowercase letters.

Prerequisites

Ensure that you have completed the following preparations in IntelliJ IDEA:

Procedure

Write a Java UDF.
1. In the Project area, right-click the module's source directory (i.e., src > main > java), and select New > MaxCompute Java.
2. In the Create new MaxCompute java class dialog box, click UDF, enter a Name, and then press Enter. For example, the Java class name is Lower.
  The Name field specifies the name of the MaxCompute Java class. If you have not created a package, you can enter packagename.classname to automatically generate a package.
3. In the code editor, enter the following code.
  The following code is an example of the UDF.
```
package <packagename>;
import com.aliyun.odps.udf.UDF;
public final class Lower extends UDF {
    public String evaluate(String s) {
        if (s == null) { 
           return null; 
        }
           return s.toLowerCase();
    }
}
```
Debug the UDF to ensure that it runs correctly.
1. In the java directory, right-click your Java class and select Run.
2. In the Run/Debug Configurations dialog box, configure the run parameters.
  - MaxCompute project: The MaxCompute project in which to run the UDF. Select local to run the UDF locally.
  - MaxCompute table: The name of the MaxCompute table to use.
  - Table columns: The columns of the MaxCompute table to use.
3. Click OK. The result is shown in the following code.
```
package wd_udf;
import com.aliyun.odps.udf.UDF;
public class Lower extends UDF {

    public String evaluate(String s) {
        if ("null".equals(s) ) {
            return null;
        }
        return s.toLowerCase();
    }
}
```
Register the MaxCompute UDF.
1. Right-click the UDF Java file and select Deploy to server....
2. In the Package a jar, submit resource and register function dialog box, configure the following parameters.
  - MaxCompute project: The MaxCompute project that contains the UDF. Keep the default value, as the plug-in automatically selects the current project.
  - Resource file: The path of the resource file required by the UDF. You can keep the default value.
  - Resource name: The resource required by the UDF. You can keep the default value.
  - Function name: The name used to call the UDF in SQL statements. For example, Lower_test.
3. Click OK to complete the UDF registration.

Call the UDF.

In the left-side navigation pane, click Project Explorer. Right-click your target MaxCompute project and select Open in Console. In the Console, enter an SQL statement to call the UDF and press Enter.

package com.aliyun.odps.udf.example;
import com.aliyun.odps.udf.UDF;
public final class Lower extends UDF {
    public String evaluate(String s) {
        if (s == null) {
            return null;
        }
        return s.toLowerCase();
    }
}

Run the following command in the Console:

select lower_test('ABC');

The following SQL statement is an example.

select Lower_test('ALIYUN');

The result shows that the Lower_test Java UDF is ready to use.

+------------+
| _c0        |
+------------+
| aliyun     |
+------------+
1 records (at most 10000 supported) fetched by instance tunnel.