使用<bind>元素創建變量
阿新 • • 發佈：2017-12-12
efault pid ron 防止 packaging oid r文件 env 屬性
在使用模糊查詢sql時，如果使用${}進行字符拼接，無法防止sql諸如問題，如果使用concat函數則只對mysql有效果，用Oracle則需要用連接符||，這樣在數據庫變的時候需要修改，不利於移植。mybatis提供元素<bind>很好能解決這個問題。
項目結構：
廢話不說，使用maven管理jar，如下：
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.example</groupId> <artifactId>maven</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>maven</name> <url>http://maven.apache.org</url><properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <dependencies> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.4.2</version> </dependency> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.4.2</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.40</version> </dependency> </dependencies> </project>
mybatis配置如下：
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration> <properties resource="resoures/db.properties" /> <!--1.配置環境 ，默認的環境id為mysql --> <environments default="mysql"> <!--1.2.配置id為mysql的數據庫環境 --> <environment id="mysql"> <!-- 使用JDBC的事務管理 --> <transactionManager type="JDBC" /> <!--數據庫連接池 --> <dataSource type="POOLED"> <!-- 數據庫驅動 --> <property name="driver" value="${jdbc.driver}" /> <!-- 連接數據庫的url --> <property name="url" value="${jdbc.url}" /> <!-- 連接數據庫的用戶名 --> <property name="username" value="${jdbc.username}" /> <!-- 連接數據庫的密碼 --> <property name="password" value="${jdbc.password}" /> </dataSource> </environment> </environments> <!--2.配置Mapper的位置 --> <mappers> <mapper resource="com/example/test/mybatis/mapper/UserMapper.xml" /> </mappers> </configuration>
數據庫配置：
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis
jdbc.username=root
jdbc.password=root
PS：註意配置文件的位置!
三種方法實現：
數據庫表格結構
javabean
package com.example.test.mybatis; public class User { private String name; private String sex; private int age; public String getName() { return name; } public void setName(String name) { this.name = name; } public String getSex() { return sex; } public void setSex(String sex) { this.sex = sex; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } @Override public String toString() { return "User [name=" + name + ", sex=" + sex + ", age=" + age + "]"; } }
session工具類：
package com.example.test.mybatis; import java.io.Reader; import org.apache.ibatis.io.Resources; import org.apache.ibatis.session.SqlSession; import org.apache.ibatis.session.SqlSessionFactory; import org.apache.ibatis.session.SqlSessionFactoryBuilder; public class MybatisUtils { private static SqlSessionFactory sqlSessionFactory = null; // 初始化SqlSessionFactory對象 static { try { // 使用MyBatis提供的Resources類加載mybatis的配置文件 Reader reader = Resources.getResourceAsReader("resoures/mybatis-config.xml"); // 構建sqlSession的工廠 sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader); } catch (Exception e) { e.printStackTrace(); } } // 獲取SqlSession對象的靜態方法 public static SqlSession getSession() { return sqlSessionFactory.openSession(); } }
mapper文件
方法一：_parameter.getName()傳參，註意參數類型為javabean User
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.example.test.mybatis.mapper.UserMapper"> <select id="findUserByName" parameterType="com.example.test.mybatis.User" resultType="com.example.test.mybatis.User"> <!--_parameter.getUsername()也可直接寫成傳入的字段屬性名，即username --> <bind name="pattern" value="‘%‘+_parameter.getName()+‘%‘" /> select * from user where name like #{pattern} </select> </mapper>
測試方式：
package com.example.test.mybatis; import java.util.List; import org.apache.ibatis.session.SqlSession; public class MybatisTest { public static void main(String[] args) { SqlSession session = MybatisUtils.getSession(); User user = new User(); user.setName("s"); List<User> list = session.selectList("com.example.test.mybatis.mapper.UserMapper.findUserByName",user); for (User u : list) { System.out.println(u); } session.close(); } }
測試結果：User [name=as, sex=男, age=1]
方法二：直接使用_parameter傳參，註意傳入的參數類型是String name
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.example.test.mybatis.mapper.UserMapper"> <select id="findUserByStrName" parameterType="String" resultType="com.example.test.mybatis.User"> <!--_parameter.getUsername()也可直接寫成傳入的字段屬性名，即username --> <bind name="username" value="‘%‘+_parameter+‘%‘" /> select * from user where name like #{username} </select> </mapper>
對應測試方法：
package com.example.test.mybatis; import java.util.List; import org.apache.ibatis.session.SqlSession; public class MybatisTest { public static void main(String[] args) { SqlSession session = MybatisUtils.getSession(); String name = "aa"; List<User> list = session.selectList("com.example.test.mybatis.mapper.UserMapper.findUserByStrName",name); for (User u : list) { System.out.println(u); } session.close(); } }
測試結果：
User [name=aa, sex=男, age=10]
User [name=aaad, sex=男, age=11]
方法三：直接用javabean的屬性傳參，註意參數類型是javabean User
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.example.test.mybatis.mapper.UserMapper"> <select id="findUserByParameterName" parameterType="com.example.test.mybatis.User" resultType="com.example.test.mybatis.User"> <!--_parameter.getUsername()也可直接寫成傳入的字段屬性名，即name --> <bind name="username" value="‘%‘+name+‘%‘" /> select * from user where name like #{username} </select> </mapper>
package com.example.test.mybatis; import java.util.List; import org.apache.ibatis.session.SqlSession; public class MybatisTest { public static void main(String[] args) { SqlSession session = MybatisUtils.getSession(); User user = new User(); user.setName("aa"); List<User> list = session.selectList("com.example.test.mybatis.mapper.UserMapper.findUserByParameterName",user); for (User u : list) { System.out.println(u); } session.close(); } }
測試結果：
User [name=aa, sex=男, age=10]
User [name=aaad, sex=男, age=11]
使用<bind>元素創建變量