Obtaining the JAR Package of the Driver and Configuring the JDK Environment

Environment preparation includes obtaining the driver JAR package and configuring the JDK environment.

Obtaining the Driver Package

Download the driver package and its verification package listed in Table 1.

**Table 1** Driver package download list
Version	Download Address
V2.0-3.x	Driver package Verification package for the driver package

To prevent a software package from being tampered with during transmission or storage, download the corresponding verification package and perform the following steps to verify the software package:

Verifying the software package integrity on a Linux server:
1. Upload the software package and verification package to the same directory on the VM.
2. Run the following command to verify the integrity of the software package:
  cat GaussDB_driver.zip.sha256 | sha256sum --check
  
  If OK is displayed in the command output, the verification is successful.
```
GaussDB_driver.zip: OK
```

Verifying the software package integrity on a Windows server:
1. Press Win+R to open the Run dialog box. Type cmd in the text box and press Enter to open the Command Prompt window.
2. Run the following command to obtain the hash value of the driver package:
  certutil -hashfile {local_directory_of_the_driver_package}\{driver_package_name} sha256
  - Replace {local_directory_of_the_driver_package} with the actual download path, for example, C:\Users.
  - Replace {driver_package_name} with the name of the downloaded driver package, for example, GaussDB_driver.zip.
  Example: certutil -hashfile C:\Users\GaussDB_driver.zip sha256
3. Compare the hash value obtained in 2 with the hash value of the verification package obtained in Table 1.
  - If they are consistent, the verification is successful.
  - If they are inconsistent, download the driver package again and repeat 1 to 3 to verify the driver package.

Decompressing the Driver Package

Decompress the obtained driver package, find the JDBC driver package GaussDB-Kernel_Database version number_OS_64bit_Jdbc.tar.gz, and decompress it. After the decompression, you will obtain the following driver packages in JAR format:

opengaussjdbc.jar: The main class name is com.huawei.opengauss.jdbc.Driver. The URL prefix of the database connection is jdbc:opengauss. This driver package is recommended. The Java code examples in this section use the opengaussjdbc.jar package by default. This driver package is used when both the PG database and GaussDB are accessed in a JVM process.

gsjdbc4.jar: The main class name is org.postgresql.Driver, and the URL prefix of the database connection is jdbc:postgresql. This driver package applies to the scenario where services are migrated from the PG database. The driver class and loading path are the same as those before the migration, but the supported APIs are different. The APIs that are not supported need to be adjusted on the service side.
gscejdbc.jar: The main class name is com.huawei.gaussdb.jdbc.Driver. The URL prefix of database connections is jdbc:gaussdb. This driver package contains the dependent libraries related to encryption and decryption that need to be loaded to the encrypted database. This driver package is recommended in encrypted scenarios. Currently, only EulerOS is supported. Before using the gscejdbc.jar driver package, set the environment variable LD_LIBRARY_PATH. For details, see "Setting Encrypted Equality Queries > Using JDBC to Operate an Encrypted Database" in Feature Guide.
gsjdbc200.jar: The main class name is com.huawei.gauss200.jdbc.Driver, and the URL prefix of the database connection is jdbc:gaussdb. This driver package applies to the scenario where services are migrated from GaussDB 200. The driver class and loading path are the same as those before the migration, but the supported APIs are different. The APIs that are not supported need to be adjusted on the service side.

The loading paths and URL prefixes of driver classes vary in different driver packages, but their functions are the same.
The JAR packages of the JDBC release package are classified by architecture. The gscejdbc.jar package can be used only when it is consistent with the deployment environment. Other JAR packages do not need to be consistent with the deployment environment.
The gsjdbc4 driver package cannot be used to operate the PG database. Although the connection can be successfully established in some versions, some API behaviors are different from those of PG JDBC, which may cause unknown errors.
The PG driver package cannot be used to operate GaussDB. Although the connection can be successfully established in some versions, some API behaviors are different from those of GaussDB JDBC, which may cause unknown errors.

Configuring the JDK Environment

JDK 1.8 must be configured on the client. JDK supports multiple platforms, such as Windows and Linux. The following uses Windows as an example to describe the configuration method:

Enter the following command in the MS-DOS window (command prompt in Windows) to check the JDK version:
```
java -version
```
Check whether JDK 1.8 has been installed. If JDK is not installed, download the installation package from the official website and install it.

Configure system environment variables.

Right-click My computer and choose Properties.
In the System window, click Advanced system settings in the navigation pane.
In the System Properties dialog box, click Environment Variables on the Advanced tab page.

In the System variables area of the Environment Variables dialog box, click New or Edit to configure system variables. For details about the variables, see Table 2.

**Table 2** Variables
Variable	Operation	Variable Value
JAVA_HOME	If the variable exists, click Edit. If the variable does not exist, click New.	Specifies the Java installation directory. Example: C:\Program Files\Java\jdk1.8.0_131
Path	Click Edit.	If JAVA_HOME is configured, add %JAVA_HOME%\bin before the variable value. If JAVA_HOME is not configured, add the full Java installation path before the variable value: C:\Program Files\Java\jdk1.8.0_131\bin
CLASSPATH	Click New.	%JAVA_HOME%\lib;%JAVA_HOME%\lib\tools.jar