使用 application.properties 文件的 Spring JDBC

Question

我正在使用 Spring JDBC 进行自我培训，并且正在学习以下教程：Spring JDBC Example。

教程很好，执行代码，我没问题。

为了简单方便，我在这里引用代码。

First class，Student（存储在 db 中的实体）：

package com.tutorialspoint;

public class Student 
{
       private Integer age;
       private String name;
       private Integer id;

       public void setAge(Integer age) 
       {
          this.age = age;
       }

       public Integer getAge() 
       {
          return age;
       }

       public void setName(String name) 
       {
          this.name = name;
       }

       public String getName() 
       {
          return name;
       }

       public void setId(Integer id) 
       {
          this.id = id;
       }

       public Integer getId() 
       {
          return id;
       }
    }

接口，StudentDAO（用于 DAO 逻辑）：

package com.tutorialspoint;

import java.util.List;
import javax.sql.DataSource;

public interface StudentDAO 
{
   /** 
      * This is the method to be used to initialize
      * database resources ie. connection.
   */
   public void setDataSource(DataSource ds);

   /** 
      * This is the method to be used to create
      * a record in the Student table.
   */
   public void create(String name, Integer age);

   /** 
      * This is the method to be used to list down
      * a record from the Student table corresponding
      * to a passed student id.
   */
   public Student getStudent(Integer id);

   /** 
      * This is the method to be used to list down
      * all the records from the Student table.
   */
   public List<Student> listStudents();

   /** 
      * This is the method to be used to delete
      * a record from the Student table corresponding
      * to a passed student id.
   */
   public void delete(Integer id);

   /** 
      * This is the method to be used to update
      * a record into the Student table.
   */
   public void update(Integer id, Integer age);
}

然后，StudentJDBCTemplate 类（用于实现 StudentDAO）：

package com.tutorialspoint;

import java.util.List;
import javax.sql.DataSource;
import org.springframework.jdbc.core.JdbcTemplate;

public class StudentJDBCTemplate implements StudentDAO 
{
   private DataSource dataSource;
   private JdbcTemplate jdbcTemplateObject;

   public void setDataSource(DataSource dataSource) 
   {
      this.dataSource = dataSource;
      this.jdbcTemplateObject = new JdbcTemplate(dataSource);
   }

   public void create(String name, Integer age) 
   {
      String SQL = "insert into Student (name, age) values (?, ?)";
      jdbcTemplateObject.update( SQL, name, age);
      System.out.println("Created Record Name = " + name + " Age = " + age);
      return;
   }

   public Student getStudent(Integer id) 
   {
      String SQL = "select * from Student where id = ?";
      Student student = jdbcTemplateObject.queryForObject(SQL, 
         new Object[]{id}, new StudentMapper());

      return student;
   }

   public List<Student> listStudents() 
   {
      String SQL = "select * from Student";
      List <Student> students = jdbcTemplateObject.query(SQL, new StudentMapper());
      return students;
   }

   public void delete(Integer id) 
   {
      String SQL = "delete from Student where id = ?";
      jdbcTemplateObject.update(SQL, id);
      System.out.println("Deleted Record with ID = " + id );
      return;
   }

   public void update(Integer id, Integer age)
   {
      String SQL = "update Student set age = ? where id = ?";
      jdbcTemplateObject.update(SQL, age, id);
      System.out.println("Updated Record with ID = " + id );
      return;
   }
}

第三类：StudentMapper（映射到 MySQL db Student）：

package com.tutorialspoint;

import java.sql.ResultSet;
import java.sql.SQLException;
import org.springframework.jdbc.core.RowMapper;

public class StudentMapper implements RowMapper<Student> 
{
   public Student mapRow(ResultSet rs, int rowNum) throws SQLException 
   {
      Student student = new Student();
      student.setId(rs.getInt("id"));
      student.setName(rs.getString("name"));
      student.setAge(rs.getInt("age"));

      return student;
   }
}

最后一个类，MainApp（运行应用程序）：

  package com.tutorialspoint;

import java.util.List;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.tutorialspoint.StudentJDBCTemplate;

public class MainApp {
   public static void main(String[] args) {
      ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");

      StudentJDBCTemplate studentJDBCTemplate = 
         (StudentJDBCTemplate)context.getBean("studentJDBCTemplate");

      System.out.println("------Records Creation--------" );
      studentJDBCTemplate.create("Zara", 11);
      studentJDBCTemplate.create("Nuha", 2);
      studentJDBCTemplate.create("Ayan", 15);

      System.out.println("------Listing Multiple Records--------" );
      List<Student> students = studentJDBCTemplate.listStudents();

      for (Student record : students) {
         System.out.print("ID : " + record.getId() );
         System.out.print(", Name : " + record.getName() );
         System.out.println(", Age : " + record.getAge());
      }

      System.out.println("----Updating Record with ID = 2 -----" );
      studentJDBCTemplate.update(2, 20);

      System.out.println("----Listing Record with ID = 2 -----" );
      Student student = studentJDBCTemplate.getStudent(2);
      System.out.print("ID : " + student.getId() );
      System.out.print(", Name : " + student.getName() );
      System.out.println(", Age : " + student.getAge());
   }
}

最后是配置数据库连接的Beans文件：

<?xml version = "1.0" encoding = "UTF-8"?>
<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-3.0.xsd ">

   <!-- Initialization for data source -->
   <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/springtraining"/>
      <property name = "username" value = "***"/>
      <property name = "password" value = "***"/>
   </bean>

   <!-- Definition for studentJDBCTemplate bean -->
   <bean id = "studentJDBCTemplate" 
      class = "com.tutorialspoint.StudentJDBCTemplate">
      <property name = "dataSource" ref = "dataSource" />    
   </bean>

</beans>

教程很清楚，如果我尝试一下，可以完美执行，没有错误，并且 MySQL Db 已正确更新。

我的问题是关于这个项目的可能变化。更具体地说：

1. 如果我想使用 application.properties 文件（如 Spring boot 给出的），这是正确的 sintax 吗？

   spring.datasource.driver-class-name=com.mysql.jdbc.Driver spring.datasource.url=jdbc:mysql://localhost:3306/springtraining spring.datasource.username=* spring.datasource.password=*

2. 如果我不想使用 RowMapper 类，是否正确使用 spring 提供的 BeanPropertyRowMapper 类？

3. 没有 Beans 文件（如果我使用，例如，application.properties，我不需要它），我如何在 MainApp 中替换这些行：

   ApplicationContext 上下文 = new ClassPathXmlApplicationContext("Beans.xml");

     StudentJDBCTemplate studentJDBCTemplate = 
        (StudentJDBCTemplate)context.getBean("studentJDBCTemplate");
   

并使应用程序可执行？

Answer 1

首先，我建议您学习如何在没有application.properties 文件的情况下进行操作。我们生活在 21 世纪，Spring-boot 允许我们使用 MySpringBootApplication 类中的数据库凭据将 jdbc dataSource 声明为 @Bean。看看怎么做here

其次，我建议不要使用jdbcTemplate，除非你没有时间。记下我的话，如果碰巧调试 - 这将是一场噩梦。所以尝试使用 纯 Jdbc 加上 spring 配置。

示例操作方法：

StudentDAO 界面

    public interface StundentDAO {

    void addStudent(String name, String surname);

    List<Student> findStudents();
}

JdbcStudentDAO 实现

    @Repository
    public class JdbcStudentDAO implements StudentDAO {

    //[IMPORTANT] import javax.sql.datasource package (?)
    private Datasource datasource;

    @Autowire
    public JdbcStudentDAO(Datasource datasource) {
        this.datasource = datasource;
    }

    @Override
    public void addStudent(String name, String surname) {
        String query = "INSERT INTO Students VALUES (?,?)";
        try(Connection connection = datasource.getConnection()) {
            try(PreparedStatement statement = connection.preparedStatement(query)) {
                statement.setString(1, name);
                statement.setString(2, surname);
                statement.executeUpdate();
            }
        } catch(SQLException e) {
            e.printStacktrace();
        }
    }

    @Override
    public List<Student> findStudents() {
        String query = "SELECT * FROM Students";
        Student student = null; //will be used soon as DTO
        List<Student> listOfStudents = null;
        try(Connection connection = datasource.getConnection()) {
            try(PreparedStatement statement = connection.preparedStatement(query)) {
                try(ResultSet rs = statement.executeQuery()) {
                    listOfStudents = new ArrayList<>();
                    while(rs.next()) {
                        student = new Student(
                            rs.getString("name");
                            rs.getString("surname");
                        );
                    }
                    listOfStudents.add(student);
                }
            }
        } catch(SQLException e) {
            e.printStacktrace();
        }
        return listOfStudents;
    }
} 

请注意，dataSource 仅进行数据库连接。（请参阅链接）

祝你好运！