Monday, 18 February 2019

Spring + JdbcTemplate + Query single column value based on two parameter example

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Querying Specific Values with Multiple Parameters in Spring JDBC

In database operations, you often need to find a specific piece of information—like an employee's name—by filtering with multiple conditions, such as their age and salary. In this guide, we use Spring JdbcTemplate to handle this efficiently with minimal code.

The SQL Logic

To fetch a single column based on two conditions, we use ? placeholders for the dynamic values. This is secure and prevents SQL injection:

        SELECT name FROM employee WHERE age = ? AND salary = ?
    

Using queryForObject

Spring's queryForObject method is perfect when you expect exactly one result. We pass three key pieces of information:

SQL String: The query defined above.
Arguments: An Object[] array containing the age and salary values.
Return Type: String.class, since we are retrieving the employee's name.

The Implementation Flow

DAO Setup: Your DAO implementation should extend JdbcDaoSupport to easily access the JdbcTemplate.
Configuration: Define your DataSource (MySQL/Oracle) in your Spring XML or Java configuration.
Execution: The container injects the data source, and your method executes the query, returning the specific string name directly from the database.

💡 Key Takeaway:

Spring JDBC handles the complex work of mapping database results to Java types, so you don't have to write messy boilerplate code!

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Spring + JdbcTemplate + Query single column value based on two parameter example

Employee.sql

CREATE DATABASE org_db;

CREATE TABLE `employee` (

  `EMPLOYEE_ID` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,

  `NAME` VARCHAR(100) NOT NULL,

  `AGE` INT(10) NOT NULL,

  `SALARY` INT(10) DEFAULT NULL,

  PRIMARY KEY (`EMPLOYEE_ID`)

) ENGINE=INNODB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;

INSERT INTO `employee` (`EMPLOYEE_ID`, `NAME`, `AGE`, `SALARY`) VALUES('1','Peter','28','80000');

INSERT INTO `employee` (`EMPLOYEE_ID`, `NAME`, `AGE`, `SALARY`) VALUES('2','John','50','40000');

INSERT INTO `employee` (`EMPLOYEE_ID`, `NAME`, `AGE`, `SALARY`) VALUES('3','David','45','20000');

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.ram.core</groupId>

    <artifactId>SpringDemo</artifactId>

    <packaging>jar</packaging>

    <version>1.0-SNAPSHOT</version>

    <name>SpringDemo</name>

    <url>http://maven.apache.org</url>

    <properties>

        <spring.version>5.0.5.RELEASE</spring.version>

    </properties>

    <dependencies>

        <dependency>

            <groupId>junit</groupId>

            <artifactId>junit</artifactId>

            <version>3.8.1</version>

            <scope>test</scope>

        </dependency>

        <!-- Spring 5 dependencies -->

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-core</artifactId>

            <version>${spring.version}</version>

        </dependency>

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-context</artifactId>

            <version>${spring.version}</version>

        </dependency>

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-jdbc</artifactId>

            <version>${spring.version}</version>

        </dependency>

        <!-- MySQL database driver -->

        <dependency>

            <groupId>mysql</groupId>

            <artifactId>mysql-connector-java</artifactId>

            <version>8.0.11</version>

        </dependency>

    </dependencies>

</project>

Employee.java

package com.ram.employee.model;

public class Employee

{

    private long employeeId;

    private String name;

    private int age;

    private int salary;

    public long getEmployeeId()

    {

        return employeeId;

    }

    public void setEmployeeId(long employeeId)

    {

        this.employeeId = employeeId;

    }

    public String getName()

    {

        return name;

    }

    public void setName(String name)

    {

        this.name = name;

    }

    public int getAge()

    {

        return age;

    }

    public void setAge(int age)

    {

        this.age = age;

    }

    public int getSalary()

    {

        return salary;

    }

    public void setSalary(int salary)

    {

        this.salary = salary;

    }

    @Override

    public String toString()

    {

        return "Employee [employeeId=" + employeeId + ", name=" + name

                + ", age=" + age + ", salary=" + salary + "]";

    }

}

EmployeeDAO.java

package com.ram.employee.dao;

public interface EmployeeDAO

{

    public String findEmployeeNameByAgeAndSalary(int age, int salary);

}

EmployeeDAOImpl.java

package com.ram.employee.dao.impl;

import org.springframework.jdbc.core.support.JdbcDaoSupport;

import com.ram.employee.dao.EmployeeDAO;

public class EmployeeDAOImpl

        extends JdbcDaoSupport implements EmployeeDAO

{

    public String findEmployeeNameByAgeAndSalary(int age, int salary)

    {

        String sql = "SELECT NAME FROM EMPLOYEE WHERE Age=? and SALARY=?";

        String name = getJdbcTemplate().queryForObject(sql,

                new Object[] { age, salary }, String.class);

        return name;

    }

}

applicationContext.xml

<beans xmlns="http://www.springframework.org/schema/beans"

    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xsi:schemaLocation="http://www.springframework.org/schema/beans

http://www.springframework.org/schema/beans/spring-beans-4.3.xsd">

    <bean id="dataSource"

        class="org.springframework.jdbc.datasource.DriverManagerDataSource">

        <property name="driverClassName" value="com.mysql.jdbc.Driver" />

        <property name="url" value="jdbc:mysql://localhost:3306/org_db" />

        <property name="username" value="root" />

        <property name="password" value="root" />

    </bean>

    <bean id="employeeDAO" class="com.ram.employee.dao.impl.EmployeeDAOImpl">

        <property name="dataSource" ref="dataSource" />

    </bean>

</beans>

App.java

package com.ram.core;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.ram.employee.dao.EmployeeDAO;

public class App

{

    public static void main(String[] args)

    {

        ApplicationContext context = new ClassPathXmlApplicationContext(

                "applicationContext.xml");

        EmployeeDAO employeeDAO = (EmployeeDAO) context

                .getBean("employeeDAO");

        String name = employeeDAO.findEmployeeNameByAgeAndSalary(50,40000);

        System.out.println("name = " + name);

    }

}

Output:

Feb 07, 2019 10:16:11 AM org.springframework.context.support.AbstractApplicationContext prepareRefresh

INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@35d176f7: startup date [Thu Feb 07 10:16:11 IST 2019]; root of context hierarchy

Feb 07, 2019 10:16:11 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

INFO: Loading XML bean definitions from class path resource [applicationContext.xml]

Loading class `com.mysql.jdbc.Driver'. This is deprecated. The new driver class is `com.mysql.cj.jdbc.Driver'. The driver is automatically registered via the SPI and manual loading of the driver class is generally unnecessary.

Feb 07, 2019 10:16:12 AM org.springframework.jdbc.datasource.DriverManagerDataSource setDriverClassName

INFO: Loaded JDBC driver: com.mysql.jdbc.Driver

Thu Feb 07 10:16:30 IST 2019 WARN: Establishing SSL connection without server's identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn't set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to 'false'. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.

name = John