Spring JDBC - 處理CLOB

---

---

概述

下面的示例將演示如何使用更新查詢和Spring JDBC更新CLOB。我們將更新學生表中的可用記錄。

學生表

CREATE TABLE Student(
   ID   INT NOT NULL AUTO_INCREMENT,
   NAME VARCHAR(20) NOT NULL,
   AGE  INT NOT NULL,
   DESCRIPTION LONGTEXT,
   PRIMARY KEY (ID)
);

語法

MapSqlParameterSource in = new MapSqlParameterSource();
in.addValue("id", id);
in.addValue("description",  new SqlLobValue(description, new DefaultLobHandler()), Types.CLOB);

String SQL = "update Student set description = :description where id = :id";
NamedParameterJdbcTemplate jdbcTemplateObject = new NamedParameterJdbcTemplate(dataSource);

jdbcTemplateObject.update(SQL, in);

其中，

• in − SqlParameterSource 物件，用於傳遞引數以更新查詢。

• SqlLobValue − 用於表示SQL BLOB/CLOB值引數的物件。

• jdbcTemplateObject − NamedParameterJdbcTemplate 物件，用於更新資料庫中的學生物件。

示例

為了理解上面提到的與Spring JDBC相關的概念，讓我們編寫一個示例，它將更新一個查詢。為了編寫我們的示例，讓我們準備好一個可執行的Eclipse IDE，並使用以下步驟建立一個Spring應用程式。

StudentDAO.java

以下是資料訪問物件介面檔案StudentDAO.java的內容。

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 update
    * a record into the Student table.
   */
   public void updateDescription(Integer id, String description);
}

Student.java

以下是Student.java檔案的內容。

package com.tutorialspoint;

// Student POJO for Student Table
public class Student {
   private Integer age;
   private String name;
   private Integer id;
   private String description;

   // setter/getter methods
   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;
   }
   public String getDescription() {
      return description;
   }
   public void setDescription(String description) {
      this.description = description;
   }
}

StudentMapper.java

以下是StudentMapper.java檔案的內容。

package com.tutorialspoint;

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

// Row Mapper Object to map Student table entry with Student Object
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"));
      student.setDescription(rs.getString("description"));
      return student;
   }
}

StudentJDBCTemplate.java

以下是為已定義的DAO介面StudentDAO實現的類檔案StudentJDBCTemplate.java。

package com.tutorialspoint;

import java.util.List;
import javax.sql.DataSource;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.namedparam.MapSqlParameterSource;
import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;
import org.springframework.jdbc.core.namedparam.SqlParameterSource;
import org.springframework.jdbc.core.simple.SimpleJdbcCall;
import org.springframework.jdbc.core.support.SqlLobValue;
import org.springframework.jdbc.support.lob.DefaultLobHandler;
import java.io.ByteArrayInputStream;
import java.sql.Types;

// DAO instance to persist Student values
public class StudentJDBCTemplate implements StudentDAO {
   private DataSource dataSource;
   private JdbcTemplate jdbcTemplateObject;
   
   // set the datasource and jdbctemplate
   public void setDataSource(DataSource dataSource) {
      this.dataSource = dataSource;
	  this.jdbcTemplateObject = new NamedParameterJdbcTemplate(dataSource);
   }
   
   // Update the description of student based on id
   public void updateDescription(Integer id, String description) {
      MapSqlParameterSource in = new MapSqlParameterSource();
      in.addValue("id", id);
      in.addValue("description",  new SqlLobValue(description, new DefaultLobHandler()), Types.CLOB);

      String SQL = "update Student set description = :description where id = :id";
      
      jdbcTemplateObject.update(SQL, in);
      System.out.println("Updated Record with ID = " + id );
   }
}

MainApp.java

以下是MainApp.java檔案的內容。

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) {
      // Create the application context by reading Beans.xml   
      ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");

      // Create the JDBCTemplate instance from spring context
      StudentJDBCTemplate studentJDBCTemplate = (StudentJDBCTemplate)context.getBean("studentJDBCTemplate");
      
      // Update the description field
      studentJDBCTemplate.updateDescription(1, "This can be a very long text upto 4 GB of size."); 
   }
}

Beans.xml

以下是配置檔案Beans.xml。

<?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.cj.jdbc.Driver"/>
      <property name = "url" value = "jdbc:mysql://:3306/TEST"/>
      <property name = "username" value = "root"/>
      <property name = "password" value = "admin"/>
   </bean>

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

輸出

建立原始檔和bean配置檔案後，讓我們執行應用程式。如果應用程式一切正常，它將列印以下訊息。

Updated Record with ID = 1

您可以透過查詢資料庫來檢查儲存的描述。