• Mybatis 动态语言 - mybatis-freemarker

    前面我们介绍了Mybatis动态SQL的使用；本篇我们介绍使用mybatis- freemarker动态语言生成动态SQL。

    如果您对Mybatis动态SQL不太了解，建议您先进行了解后再阅读本篇，可以参考：

    Mybatis 动态SQL – 使用if,where标签动态生成条件语句

    Mybatis 动态SQL – 使用if,set标签动态生成更新语句

    Mybatis 动态SQL – 使用choose标签动态生成条件语句

    Mybatis 动态SQL – 使用choose标签动态生成更新语句

    Mybatis 动态SQL – 使用trim标签替代where,set标签

    Mybatis 动态SQL - 使用foreach标签查询数据、批量新增、批量修改、删除数据

    一、数据准备

    这里我们直接使用脚本初始化数据库中的数据

    1. -- 如果数据库不存在则创建数据库
    2. CREATE DATABASE IF NOT EXISTS demo DEFAULT CHARSET utf8;
    3. -- 切换数据库
    4. USE demo;
    5. -- 创建用户表
    6. CREATE TABLE IF NOT EXISTS T_TEACHER(
    7.   ID INT PRIMARY KEY COMMENT '教师编号',
    8.   TEACHER_NAME VARCHAR(64) NOT NULL COMMENT '教师名称',
    9.   DEPARTMENT VARCHAR(16) NOT NULL COMMENT '所属部门',
    10.   BIRTH DATE NOT NULL COMMENT '出生年月',
    11.   DEGREE VARCHAR(16) NOT NULL COMMENT '学历(ZK:专科, BK:本科, YJS:研究生, BS:博士)'
    12. );
    13. -- 插入用户数据
    14. INSERT INTO T_TEACHER(ID, TEACHER_NAME, DEPARTMENT, BIRTH, DEGREE)
    15. VALUES(1, '张三1', '001', '1990-06-12', 'BK'),
    16.       (2, '李四1', '002', '1992-05-10', 'BK'),
    17.       (3, '张三2', '003', '1988-01-15', 'YJS'),
    18.       (4, '李四2', '001', '1979-03-10', 'BK'),
    19.       (5, '李四3', '003', '1995-08-16', 'YJS');

    创建了一个名称为demo的数据库；并在库里创建了名称为T_TEACHER的教师表并向表中插入了数据

    二、环境准备

    1、添加依赖

    1. <dependency>
    2.     <groupId>org.mybatis.scriptinggroupId>
    3.     <artifactId>mybatis-freemarkerartifactId>
    4.     <version>1.2.4version>
    5. dependency>

    2、创建实体类

    在cn.horse.demo下创建TeacherInfo、TeacherInfoQuery实体类：

    TeacherInfo类：

    1. package cn.horse.demo;
    2.  
    3. import java.time.LocalDate;
    4.  
    5. public class TeacherInfo {
    6.     private Integer id;
    7.     private String name;
    8.     private String department;
    9.     private LocalDate birth;
    10.     private String degree;
    11.  
    12.     public void setId(Integer id) {
    13.         this.id = id;
    14.     }
    15.  
    16.     public Integer getId() {
    17.         return id;
    18.     }
    19.  
    20.     public void setName(String name) {
    21.         this.name = name;
    22.     }
    23.  
    24.     public String getName() {
    25.         return name;
    26.     }
    27.  
    28.     public void setDepartment(String department) {
    29.         this.department = department;
    30.     }
    31.  
    32.     public String getDepartment() {
    33.         return department;
    34.     }
    35.  
    36.     public void setBirth(LocalDate birth) {
    37.         this.birth = birth;
    38.     }
    39.  
    40.     public LocalDate getBirth() {
    41.         return birth;
    42.     }
    43.  
    44.     public void setDegree(String degree) {
    45.         this.degree = degree;
    46.     }
    47.  
    48.     public String getDegree() {
    49.         return degree;
    50.     }
    51.  
    52.     @Override
    53.     public String toString() {
    54.         StringBuilder stringBuilder = new StringBuilder();
    55.         stringBuilder.append("{ ");
    56.         stringBuilder.append("id: ");
    57.         stringBuilder.append(this.id);
    58.         stringBuilder.append(", ");
    59.         stringBuilder.append("name: ");
    60.         stringBuilder.append(this.name);
    61.         stringBuilder.append(", ");
    62.         stringBuilder.append("department: ");
    63.         stringBuilder.append(this.department);
    64.         stringBuilder.append(", ");
    65.         stringBuilder.append("birth: ");
    66.         stringBuilder.append(this.birth);
    67.         stringBuilder.append(", ");
    68.         stringBuilder.append("degree: ");
    69.         stringBuilder.append(this.degree);
    70.         stringBuilder.append(" }");
    71.         return stringBuilder.toString();
    72.     }
    73. }

    TeacherInfoQuery类：

    1. package cn.horse.demo;
    2.  
    3. public class TeacherInfoQuery {
    4.  
    5.     private String department;
    6.     private String degree;
    7.  
    8.     public void setDepartment(String department) {
    9.         this.department = department;
    10.     }
    11.  
    12.     public String getDepartment() {
    13.         return department;
    14.     }
    15.  
    16.     public void setDegree(String degree) {
    17.         this.degree = degree;
    18.     }
    19.  
    20.     public String getDegree() {
    21.         return degree;
    22.     }
    23. }

    3、Mapper配置文件

    在resources的目录下新建TeacherInfoMapper.xml配置文件

    1. "1.0" encoding="UTF-8" ?>
    2. mapper
    3.         PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
    4.         "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
    5. <mapper namespace="cn.horse.demo.TeacherInfoMapper">
    6.  
    7. mapper>

    4、动态语言配置

    在resources下新建mybatis-config.xml配置文件，配置freemarker默认的脚本语言，并引入TeacherInfoMapper.xml配置文件

    1. "1.0" encoding="UTF-8" ?>
    2. configuration
    3.         PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
    4.         "http://mybatis.org/dtd/mybatis-3-config.dtd">
    5. <configuration>
    6.     <settings>
    7.         <setting name="logImpl" value="JDK_LOGGING"/>
    8.         <setting name="defaultScriptingLanguage" value="org.mybatis.scripting.freemarker.FreeMarkerLanguageDriver"/>
    9.     settings>
    10.  
    11.     <environments default="development">
    12.         <environment id="development">
    13.             <transactionManager type="JDBC"/>
    14.             <dataSource type="POOLED">
    15.                 <property name="driver" value="org.gjt.mm.mysql.Driver"/>
    16.                 <property name="url" value="jdbc:mysql://localhost:3306/demo?useUnicode=true&useSSL=false&characterEncoding=utf8"/>
    17.                 <property name="username" value="root"/>
    18.                 <property name="password" value="horse"/>
    19.             dataSource>
    20.         environment>
    21.     environments>
    22.  
    23.     <mappers>
    24.         <mapper resource="demo/TeacherInfoMapper.xml" />
    25.     mappers>
    26. configuration>

    其中用于配置freemarker作为默认的动态语言

    5、日志配置

    在resources的目录下新建logging.properties配置文件

    1. handlers=java.util.logging.ConsoleHandler
    2. .level=INFO
    3.  
    4. cn.horse.demo.TeacherInfoMapper.level=FINER
    5. java.util.logging.ConsoleHandler.level=ALL
    6. java.util.logging.ConsoleHandler.formatter=java.util.logging.SimpleFormatter
    7. java.util.logging.SimpleFormatter.format=%1$tY-%1$tm-%1$td %1$tT.%1$tL %4$s %3$s - %5$s%6$s%n

    在cn.horse.demo下新建JdkLogConfig类：

    JdkLogConfig类：

    1. package cn.horse.demo;
    2.  
    3. import java.io.IOException;
    4. import java.io.InputStream;
    5. import java.util.logging.LogManager;
    6.  
    7. public class JdkLogConfig {
    8.  
    9.     public JdkLogConfig() {
    10.         try {
    11.             InputStream inputStream = ClassLoader.getSystemClassLoader().getResourceAsStream("logging.properties");
    12.             LogManager.getLogManager().readConfiguration(inputStream);
    13.         } catch (IOException e) {
    14.             throw new RuntimeException(e);
    15.         }
    16.     }
    17. }

    6、会话工具类

    在cn.horse.demo包下新建SqlSessionUtils工具类

    1. package cn.horse.demo;
    2.  
    3. import org.apache.ibatis.session.SqlSession;
    4. import org.apache.ibatis.session.SqlSessionFactory;
    5. import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    6.  
    7. import java.io.InputStream;
    8. import java.util.Objects;
    9.  
    10. public class SqlSessionUtils {
    11.  
    12.     private static final SqlSessionFactory sqlSessionFactory;
    13.     static {
    14.         // 读取mybatis配置文件
    15.         InputStream inputStream = ClassLoader.getSystemClassLoader().getResourceAsStream("mybatis-config.xml");
    16.         // 根据配置创建SqlSession工厂
    17.         sqlSessionFactory = new SqlSessionFactoryBuilder()
    18.                 .build(inputStream);
    19.     }
    20.  
    21.     /**
    22.      * 开启会话
    23.      * @return
    24.      */
    25.     public static SqlSession openSession() {
    26.         return sqlSessionFactory.openSession();
    27.     }
    28.  
    29.     /**
    30.      * 关闭会话
    31.      * @param sqlSession
    32.      */
    33.     public static void closeSession(SqlSession sqlSession) {
    34.         if(Objects.nonNull(sqlSession)) {
    35.             sqlSession.close();
    36.         }
    37.     }
    38. }

    7、启动程序配置

    1. package cn.horse.demo;
    2.  
    3. import org.apache.ibatis.session.SqlSession;
    4.  
    5. import java.util.List;
    6.  
    7. public class Main {
    8.     public static void main(String[] args) {
    9.         // 引入JDK日志配置
    10.         System.setProperty("java.util.logging.config.class", "cn.horse.demo.JdkLogConfig");
    11.     }
    12.  
    13.     private static void find(String statement, TeacherInfoQuery query) {
    14.         SqlSession sqlSession = null;
    15.         try {
    16.             sqlSession = SqlSessionUtils.openSession();
    17.             List teacherInfoList = sqlSession.selectList(statement, query);
    18.             for (TeacherInfo teacherInfo: teacherInfoList) {
    19.                 System.out.println(teacherInfo);
    20.             }
    21.         } finally {
    22.             SqlSessionUtils.closeSession(sqlSession);
    23.         }
    24.     }
    25.  
    26.     private static void insert(String statement, List teacherInfoList) {
    27.         SqlSession sqlSession = null;
    28.         try {
    29.             sqlSession = SqlSessionUtils.openSession();
    30.             sqlSession.insert(statement, teacherInfoList);
    31.             sqlSession.commit();
    32.         } finally {
    33.             SqlSessionUtils.closeSession(sqlSession);
    34.         }
    35.     }
    36.  
    37.     private static void update(String statement, TeacherInfo teacherInfo) {
    38.         SqlSession sqlSession = null;
    39.         try {
    40.             sqlSession = SqlSessionUtils.openSession();
    41.             sqlSession.update(statement, teacherInfo);
    42.             sqlSession.commit();
    43.         } finally {
    44.             SqlSessionUtils.closeSession(sqlSession);
    45.         }
    46.     }
    47.  
    48.     private static void delete(String statement, List idList) {
    49.         SqlSession sqlSession = null;
    50.         try {
    51.             sqlSession = SqlSessionUtils.openSession();
    52.             sqlSession.delete(statement, idList);
    53.             sqlSession.commit();
    54.         } finally {
    55.             SqlSessionUtils.closeSession(sqlSession);
    56.         }
    57.     }
    58. }

    三、查询数据

    在TeacherInfoMapper.xml配置文件中新增findByQuery查询语句：

    1. <select id="find" resultType="cn.horse.demo.TeacherInfo">
    2.     SELECT
    3.         ID,
    4.         TEACHER_NAME name,
    5.         DEPARTMENT,
    6.         BIRTH,
    7.         DEGREE
    8.     FROM T_TEACHER
    9.     WHERE 1 = 1
    10.     
    11.         <#if degree?? && '' != degree>
    12.             AND DEGREE = <@p name='degree'/>
    13.         
    14.         <#if department?? && '' != department>
    15.             AND DEPARTMENT = <@p name='department'/>
    16.         
    17.     ]]>
    18. select>

    #if类似于标签，第一个标签代表的是degree不为null并且不为空字符串，第二个标签代表的是department不为null并且不为空字符串；

    测试：

    1. // 引入JDK日志配置
    2. System.setProperty("java.util.logging.config.class", "cn.horse.demo.JdkLogConfig");
    3.  
    4. // 查询学历为本科的教师
    5. TeacherInfoQuery query = new TeacherInfoQuery();
    6. query.setDegree("BK");
    7. find("cn.horse.demo.TeacherInfoMapper.find", query);

    执行后的结果如下：

    四、批量插入数据

    在TeacherInfoMapper.xml配置文件中新增insert插入语句：

    1. <insert id="insert">
    2.     INSERT INTO T_TEACHER(ID, TEACHER_NAME, DEPARTMENT, BIRTH, DEGREE)
    3.     VALUES
    4.     
    5.         <#list list as teacherInfo>
    6.             (<@p value=teacherInfo.id/>,
    7.              <@p value=teacherInfo.name/>,
    8.              <@p value=teacherInfo.department/>,
    9.              <@p value=teacherInfo.birth/>,
    10.              <@p value=teacherInfo.degree/>)
    11.             <#if teacherInfo_has_next>,
    12.         
    13.     ]]>
    14. insert>

    测试： 

    1. // 引入JDK日志配置
    2. System.setProperty("java.util.logging.config.class", "cn.horse.demo.JdkLogConfig");
    3.  
    4. List teacherInfoList = new ArrayList<>();
    5. TeacherInfo teacherInfo1 = new TeacherInfo();
    6. teacherInfo1.setId(11);
    7. teacherInfo1.setName("张三11");
    8. teacherInfo1.setDepartment("001");
    9. teacherInfo1.setBirth(LocalDate.of(1988, 5, 20));
    10. teacherInfo1.setDegree("BK");
    11. teacherInfoList.add(teacherInfo1);
    12.  
    13. TeacherInfo teacherInfo2 = new TeacherInfo();
    14. teacherInfo2.setId(12);
    15. teacherInfo2.setName("李四12");
    16. teacherInfo2.setDepartment("003");
    17. teacherInfo2.setBirth(LocalDate.of(1989, 8, 10));
    18. teacherInfo2.setDegree("ZK");
    19. teacherInfoList.add(teacherInfo2);
    20. insert("cn.horse.demo.TeacherInfoMapper.insert", teacherInfoList);

    执行的结果如下：

    五、更新数据

    在TeacherInfoMapper.xml配置文件中新增update更新语句：

    1. <update id="update">
    2.     UPDATE T_TEACHER
    3.     SET
    4.     
    5.         ID = <@p name='id'/>
    6.         <#if name?? && '' != name>
    7.             , TEACHER_NAME = <@p name='name'/>
    8.         
    9.         <#if department?? && '' != department>
    10.             , DEPARTMENT = <@p name='department'/>
    11.         
    12.         <#if birth??>
    13.             , BIRTH = <@p name='birth'/>
    14.         
    15.         <#if degree?? && '' != degree>
    16.             , DEGREE = <@p name='degree'/>
    17.         
    18.     ]]>
    19.     WHERE ID =  ]]>
    20. update>

    测试： 

    1. // 引入JDK日志配置
    2. System.setProperty("java.util.logging.config.class", "cn.horse.demo.JdkLogConfig");
    3.  
    4. TeacherInfo teacherInfo = new TeacherInfo();
    5. teacherInfo.setId(11);
    6. teacherInfo.setName("张三22");
    7. update("cn.horse.demo.TeacherInfoMapper.update", teacherInfo);

    执行的结果如下：

    六、批量删除数据

    在TeacherInfoMapper.xml配置文件中新增delete删除语句：

    1. <delete id="delete">
    2.     DELETE FROM T_TEACHER
    3.     WHERE ID IN (
    4.         
    5.             <#list list as id>
    6.                 <@p value=id/>
    7.                 <#if id_has_next>,
    8.             
    9.         ]]>
    10.     )
    11. delete>

    测试： 

    1. // 引入JDK日志配置
    2. System.setProperty("java.util.logging.config.class", "cn.horse.demo.JdkLogConfig");
    3.  
    4. delete("cn.horse.demo.TeacherInfoMapper.delete", Arrays.asList(11, 12));

    执行的结果如下：

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  • 原文地址：https://blog.csdn.net/m1729339749/article/details/132830317