org.springframework.jdbc.core.PreparedStatementSetter
接口充當JdbcTemplate
類使用的一般回調接口。該接口在JdbcTemplate
類提供的PreparedStatement
上設置了使用相同SQL的批處理中的每個更新的值。實現負責設置必要的參數。已經提供帶有占位符的SQL,使用此接口比PreparedStatementCreator
更容易:JdbcTemplate
將創建PreparedStatement
,回調僅負責設置參數值。
接口的聲明
以下是org.springframework.jdbc.core.PreparedStatementSetter
接口的聲明 -
public interface PreparedStatementSetter
用法
步驟1 - 使用配置的數據源創建一個JdbcTemplate
對象。
步驟2 - 使用JdbcTemplate
對象方法進行數據庫操作,同時傳遞PreparedStatementSetter
對象來替換查詢中的占位符。
實例
以下示例將演示如何使用JdbcTemplate
類和PreparedStatementSetter
接口進行讀取查詢。這里我們將從student
表中讀取記錄。
語法
final String SQL = "select * from Student where id = ? "; List <Student> students = jdbcTemplateObject.query(SQL, new PreparedStatementSetter() { public void setValues(PreparedStatement preparedStatement) throws SQLException { preparedStatement.setInt(1, id); } }, new StudentMapper());
在上面示例(語法)代碼中 -
- SQL - 選擇查詢語句來來讀取學生記錄信息。
- jdbcTemplateObject -
StudentJDBCTemplate
對象從數據庫中讀取Student
對象。 - PreparedStatementSetter -
PreparedStatementSetter
對象在查詢中設置參數。 - StudentMapper -
StudentMapper
是一個RowMapper對象,用於將每個獲取的記錄映射到學生對象。
實例項目
要了解上述與Spring JDBC相關的概念,下面我們編寫一個select查詢語句的示例。打開Eclipse IDE,並按照以下步驟創建一個Spring應用程序,這里創建一個名稱為:PreparedStatementSetter 的項目。
步驟說明
- 參考第一個Spring JDBC項目來創建一個Maven項目 - http://www.yiibai.com/springjdbc/first_application.html
- 更新bean配置並運行應用程序。
完整的項目結構如下所示 -
以下是Maven配置文件:pom.xml的代碼內容:
<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/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.yiibai</groupId> <artifactId>PreparedStatementSetter</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>PreparedStatementSetter</name> <url>http://maven.apache.org</url> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>3.8.1</version> <scope>test</scope> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.40</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-jdbc</artifactId> <version>4.1.0.RELEASE</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>4.1.4.RELEASE</version> </dependency> </dependencies> </project>
以下是數據訪問對象接口文件:StudentDAO.java的內容:
package com.yiibai; 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 list down all the records from the * Student table. */ public List<Student> listStudents(); public Student getStudent(Integer id); public void create(String name, Integer age); }
以下是文件:Student.java的代碼內容:
package com.yiibai; 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; } }
以下是文件:StudentMapper.java的代碼內容:
package com.yiibai; 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; } }
實現類StudentJDBCTemplate.java
實現了定義的DAO接口 - StudentDAO.java
,以下是文件:StudentJDBCTemplate.java的代碼內容:
package com.yiibai; import java.sql.PreparedStatement; import java.util.List; import javax.sql.DataSource; import org.springframework.jdbc.core.JdbcTemplate; import org.springframework.jdbc.core.ParameterizedPreparedStatementSetter; import org.springframework.jdbc.core.PreparedStatementSetter; import java.sql.SQLException; 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 List<Student> listStudents() { String SQL = "select * from Student"; List<Student> students = jdbcTemplateObject.query(SQL, new StudentMapper()); return students; } public void create(String name, Integer age) { // TODO Auto-generated method stub String insertQuery = "insert into student (name, age) values (?, ?)"; jdbcTemplateObject.update(insertQuery, name, age); System.out.println("Created Record Name = " + name + " Age = " + age); return; } public Student getStudent(final Integer id) { final String SQL = "select * from Student where id = ? "; List<Student> students = jdbcTemplateObject.query(SQL, new PreparedStatementSetter() { public void setValues(PreparedStatement preparedStatement) throws SQLException { preparedStatement.setInt(1, id); } }, new StudentMapper()); return students.get(0); } }
以下是文件:MainApp.java的代碼內容:
package com.yiibai; import java.util.ArrayList; import java.util.List; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; import com.yiibai.StudentJDBCTemplate; public class MainApp { public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext("application-beans.xml"); StudentJDBCTemplate studentJDBCTemplate = (StudentJDBCTemplate) context.getBean("studentJDBCTemplate"); System.out.println("------Records Creation--------"); studentJDBCTemplate.create("Maxsu", 21); studentJDBCTemplate.create("Curry", 22); studentJDBCTemplate.create("Suzend", 23); System.out.println("------Get Student Info by ID=1 --------"); Student student = studentJDBCTemplate.getStudent(1); System.out.print("ID : " + student.getId()); System.out.println(", Age : " + student.getAge()); 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()); } } }
以下是文件:application-beans.xml的代碼內容:
<?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/test?characterEncoding=utf8&useSSL=true" /> <property name="username" value="root" /> <property name="password" value="123456" /> </bean> <!-- Definition for studentJDBCTemplate bean --> <bean id="studentJDBCTemplate" class="com.yiibai.StudentJDBCTemplate"> <property name="dataSource" ref="dataSource" /> </bean> </beans>
注意: application-beans.xml 文件的位置是:{workspace}/fistapp/src/main/java 目錄,如果放置錯了,程序可能會因為找不到此配置文件而出錯。
完成創建源代碼和bean和數據庫連接信息的文件配置后,運行應用程序。這里先簡單說明一下運行的步驟,在項目名稱(PreparedStatementSetter)上點擊右鍵,在彈出的菜單中選擇:【Run As】-> 【Maven test】
在運行測試成功后,應該會輸出類似以下內容(含有 BUILD SUCCESS 的信息) 。
接下來,點擊類文件:MainApp.java 選擇【Run As】->【Java Application】,如果應用程序一切正常,這將打印以下結果:
------Records Creation--------
Created Record Name = Maxsu Age = 21
Created Record Name = Curry Age = 22
Created Record Name = Suzend Age = 23
------Get Student Info by ID=1 --------
ID : 1, Age : 21
------Listing Multiple Records--------
ID : 1, Name : Maxsu, Age : 21
ID : 2, Name : Curry, Age : 22
ID : 3, Name : Suzend, Age : 23