• Mybatis 使用typeHandler自定义类型转换

    之前我们介绍了使用Mybatis完成数据的增删改查操作；本篇我们介绍使用Mybatis提供的typeHandler自定义类型转换。

    如果您对Mybatis的增删改查操作不太了解，可以参考：

    Mybatis 查询数据icon-default.png?t=N7T8https://blog.csdn.net/m1729339749/article/details/132469672Mybatis 插入、修改、删除icon-default.png?t=N7T8https://blog.csdn.net/m1729339749/article/details/132601345

    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 ENUM('ZK','BK','YJS','BS') 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

    注意：教师表中的DEGREE字段是枚举类型

    二、环境搭建

    1、创建实体类

    在cn.horse.demo下创建TeacherInfo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 Degree 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(Degree degree) {
    45.         this.degree = degree;
    46.     }
    47.  
    48.     public Degree 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. }

    Degree枚举类：

    1. package cn.horse.demo;
    2.  
    3. public enum Degree {
    4.  
    5.     // 专科
    6.     COLLEGE,
    7.     // 本科
    8.     BACHELOR,
    9.     // 研究生
    10.     GRADUATE,
    11.     // 博士
    12.     DOCTORAL
    13. }

    2、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.     <resultMap id="teacherInfoMap" type="cn.horse.demo.TeacherInfo">
    8.         <result column="ID" property="id" />
    9.         <result column="TEACHER_NAME" property="name" />
    10.         <result column="DEPARTMENT" property="department" />
    11.         <result column="BIRTH" property="birth" />
    12.         <result column="DEGREE" property="degree" />
    13.     resultMap>
    14.  
    15.     <select id="findAll" resultMap="teacherInfoMap">
    16.         SELECT
    17.             ID,
    18.             TEACHER_NAME,
    19.             DEPARTMENT,
    20.             BIRTH,
    21.             DEGREE
    22.         FROM T_TEACHER
    23.     select>
    24.  
    25.     <insert id="insert" parameterType="cn.horse.demo.TeacherInfo">
    26.         INSERT INTO T_TEACHER(ID, TEACHER_NAME, DEPARTMENT, BIRTH, DEGREE)
    27.         VALUES(#{id}, #{name}, #{department}, #{birth}, #{degree})
    28.     insert>
    29. mapper>

    3、引入配置文件

    在resources下新建mybatis-config.xml配置文件，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.     settings>
    9.  
    10.     <environments default="development">
    11.         <environment id="development">
    12.             <transactionManager type="JDBC"/>
    13.             <dataSource type="POOLED">
    14.                 <property name="driver" value="org.gjt.mm.mysql.Driver"/>
    15.                 <property name="url" value="jdbc:mysql://localhost:3306/demo?useUnicode=true&useSSL=false&characterEncoding=utf8"/>
    16.                 <property name="username" value="root"/>
    17.                 <property name="password" value="horse"/>
    18.             dataSource>
    19.         environment>
    20.     environments>
    21.  
    22.     <mappers>
    23.         <mapper resource="demo/TeacherInfoMapper.xml" />
    24.     mappers>
    25. configuration>

    4、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. }

    5、JDK 日志系统配置

    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、启动程序配置

    1. package cn.horse.demo;
    2.  
    3. import org.apache.ibatis.session.SqlSession;
    4.  
    5. import java.time.LocalDate;
    6. import java.util.List;
    7.  
    8. public class Main {
    9.     public static void main(String[] args) {
    10.         // 引入JDK日志配置
    11.         System.setProperty("java.util.logging.config.class", "cn.horse.demo.JdkLogConfig");
    12.     }
    13. }

    三、数据转换存在的问题

    1、例子：查询教师列表

    添加查询教师列表的静态方法

    1. private static void findAll(String statement) {
    2.     SqlSession sqlSession = null;
    3.     try {
    4.         sqlSession = SqlSessionUtils.openSession();
    5.         List teacherInfoList = sqlSession.selectList(statement);
    6.         for (TeacherInfo teacherInfo: teacherInfoList) {
    7.             System.out.println(teacherInfo);
    8.         }
    9.     } finally {
    10.         SqlSessionUtils.closeSession(sqlSession);
    11.     }
    12. }

    调用查询教师列表的方法

    1. // 引入JDK日志配置
    2. System.setProperty("java.util.logging.config.class", "cn.horse.demo.JdkLogConfig");
    3. findAll("cn.horse.demo.TeacherInfoMapper.findAll");

    执行后的结果如下：

    1.  2023-09-04 16:26:40.114 详细 cn.horse.demo.TeacherInfoMapper.findAll - ==>  Preparing: SELECT ID, TEACHER_NAME, DEPARTMENT, BIRTH, DEGREE FROM T_TEACHER 
    2. 2023-09-04 16:26:40.163 详细 cn.horse.demo.TeacherInfoMapper.findAll - ==> Parameters: 
    3. 2023-09-04 16:26:40.176 较详细 cn.horse.demo.TeacherInfoMapper.findAll - <==    Columns: ID, TEACHER_NAME, DEPARTMENT, BIRTH, DEGREE
    4. 2023-09-04 16:26:40.180 较详细 cn.horse.demo.TeacherInfoMapper.findAll - <==        Row: 1, 张三1, 001, 1990-06-12, BK
    5. Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException: 
    6. ### Error querying database.  Cause: org.apache.ibatis.executor.result.ResultMapException: Error attempting to get column 'DEGREE' from result set.  Cause: java.lang.IllegalArgumentException: No enum constant cn.horse.demo.Degree.BK
    7. ### The error may exist in demo/TeacherInfoMapper.xml
    8. ### The error may involve cn.horse.demo.TeacherInfoMapper.findAll
    9. ### The error occurred while handling results
    10. ### SQL: SELECT             ID,             TEACHER_NAME,             DEPARTMENT,             BIRTH,             DEGREE         FROM T_TEACHER
    11. ### Cause: org.apache.ibatis.executor.result.ResultMapException: Error attempting to get column 'DEGREE' from result set.  Cause: java.lang.IllegalArgumentException: No enum constant cn.horse.demo.Degree.BK
    12. 	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
    13. 	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:150)
    14. 	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)
    15. 	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:136)
    16. 	at cn.horse.demo.Main.findAll(Main.java:29)
    17. 	at cn.horse.demo.Main.main(Main.java:12)
    18. Caused by: org.apache.ibatis.executor.result.ResultMapException: Error attempting to get column 'DEGREE' from result set.  Cause: java.lang.IllegalArgumentException: No enum constant cn.horse.demo.Degree.BK
    19. 	at org.apache.ibatis.type.BaseTypeHandler.getResult(BaseTypeHandler.java:68)
    20. 	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.getPropertyMappingValue(DefaultResultSetHandler.java:467)
    21. 	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.applyPropertyMappings(DefaultResultSetHandler.java:436)
    22. 	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.getRowValue(DefaultResultSetHandler.java:399)
    23. 	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValuesForSimpleResultMap(DefaultResultSetHandler.java:351)
    24. 	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValues(DefaultResultSetHandler.java:326)
    25. 	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSet(DefaultResultSetHandler.java:299)
    26. 	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSets(DefaultResultSetHandler.java:192)
    27. 	at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:64)
    28. 	at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:79)
    29. 	at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:63)
    30. 	at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:324)
    31. 	at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156)
    32. 	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109)
    33. 	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:83)
    34. 	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148)
    35. 	... 4 more
    36. Caused by: java.lang.IllegalArgumentException: No enum constant cn.horse.demo.Degree.BK
    37. 	at java.base/java.lang.Enum.valueOf(Enum.java:273)
    38. 	at org.apache.ibatis.type.EnumTypeHandler.getNullableResult(EnumTypeHandler.java:49)
    39. 	at org.apache.ibatis.type.EnumTypeHandler.getNullableResult(EnumTypeHandler.java:26)
    40. 	at org.apache.ibatis.type.BaseTypeHandler.getResult(BaseTypeHandler.java:66)
    41. 	... 19 more

    分析：

    从数据库表中查询出来的学历数据无法在Degree学历枚举类型中找到

    2、例子：新增教师

    添加新增教师的静态方法

    1. private static void insert(String statement, TeacherInfo teacherInfo) {
    2.     SqlSession sqlSession = null;
    3.     try {
    4.         sqlSession = SqlSessionUtils.openSession();
    5.         sqlSession.insert(statement, teacherInfo);
    6.         sqlSession.commit();
    7.     } finally {
    8.         SqlSessionUtils.closeSession(sqlSession);
    9.     }
    10. }

    调用新增教师的方法

    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("张三1");
    7. teacherInfo.setDepartment("001");
    8. teacherInfo.setBirth(LocalDate.of(1998, 10, 20));
    9. teacherInfo.setDegree(Degree.DOCTORAL);
    10. insert("cn.horse.demo.TeacherInfoMapper.insert", teacherInfo);

    执行后的结果如下：

    1. 2023-09-04 16:28:58.817 详细 cn.horse.demo.TeacherInfoMapper.insert - ==>  Preparing: INSERT INTO T_TEACHER(ID, TEACHER_NAME, DEPARTMENT, BIRTH, DEGREE) VALUES(?, ?, ?, ?, ?) 
    2. 2023-09-04 16:28:58.875 详细 cn.horse.demo.TeacherInfoMapper.insert - ==> Parameters: 11(Integer), 张三1(String), 001(String), 1998-10-20(Date), DOCTORAL(String)
    3. Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException: 
    4. ### Error updating database.  Cause: java.sql.SQLException: Data truncated for column 'DEGREE' at row 1
    5. ### The error may involve cn.horse.demo.TeacherInfoMapper.insert-Inline
    6. ### The error occurred while setting parameters
    7. ### SQL: INSERT INTO T_TEACHER(ID, TEACHER_NAME, DEPARTMENT, BIRTH, DEGREE)         VALUES(?, ?, ?, ?, ?)
    8. ### Cause: java.sql.SQLException: Data truncated for column 'DEGREE' at row 1
    9. 	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
    10. 	at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:200)
    11. 	at org.apache.ibatis.session.defaults.DefaultSqlSession.insert(DefaultSqlSession.java:185)
    12. 	at cn.horse.demo.Main.insert(Main.java:40)
    13. 	at cn.horse.demo.Main.main(Main.java:20)
    14. Caused by: java.sql.SQLException: Data truncated for column 'DEGREE' at row 1
    15. 	at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:965)
    16. 	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3933)
    17. 	at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3869)
    18. 	at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2524)
    19. 	at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2675)
    20. 	at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2465)
    21. 	at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1915)
    22. 	at com.mysql.jdbc.PreparedStatement.execute(PreparedStatement.java:1254)
    23. 	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    24. 	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
    25. 	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    26. 	at java.base/java.lang.reflect.Method.invoke(Method.java:568)
    27. 	at org.apache.ibatis.logging.jdbc.PreparedStatementLogger.invoke(PreparedStatementLogger.java:59)
    28. 	at jdk.proxy3/jdk.proxy3.$Proxy3.execute(Unknown Source)
    29. 	at org.apache.ibatis.executor.statement.PreparedStatementHandler.update(PreparedStatementHandler.java:46)
    30. 	at org.apache.ibatis.executor.statement.RoutingStatementHandler.update(RoutingStatementHandler.java:74)
    31. 	at org.apache.ibatis.executor.SimpleExecutor.doUpdate(SimpleExecutor.java:50)
    32. 	at org.apache.ibatis.executor.BaseExecutor.update(BaseExecutor.java:117)
    33. 	at org.apache.ibatis.executor.CachingExecutor.update(CachingExecutor.java:76)
    34. 	at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:198)
    35. 	... 3 more

    分析：

    Degree学历枚举类型的数据存储到数据库表中的字段时，无法将枚举类型的数据转换成数据库表中字段能够存储的数据

    四、自定义数据类型转换

    上面的两个示例中，我们从库中查询数据(读库)或者向库中插入数据(写库)都存在数据转换的问题，mybatis给我们提供了TypeHandler扩展，可以根据类型自定义读写库时数据的转换。

    自定义DegreeTypeHandler：

    1. package cn.horse.demo;
    2.  
    3. import org.apache.ibatis.type.JdbcType;
    4. import org.apache.ibatis.type.TypeHandler;
    5.  
    6. import java.sql.CallableStatement;
    7. import java.sql.PreparedStatement;
    8. import java.sql.ResultSet;
    9. import java.sql.SQLException;
    10.  
    11. public class DegreeTypeHandler implements TypeHandler {
    12.     @Override
    13.     public void setParameter(PreparedStatement ps, int i, Degree parameter, JdbcType jdbcType) throws SQLException {
    14.         ps.setString(i, formatDegree(parameter));
    15.     }
    16.  
    17.     private String formatDegree(Degree degree) {
    18.         switch (degree) {
    19.             case COLLEGE:
    20.                 return "ZK";
    21.             case BACHELOR:
    22.                 return "BK";
    23.             case GRADUATE:
    24.                 return "YJS";
    25.             case DOCTORAL:
    26.                 return "BS";
    27.         }
    28.         return null;
    29.     }
    30.  
    31.     @Override
    32.     public Degree getResult(ResultSet rs, String columnName) throws SQLException {
    33.         return parseDegree(rs.getString(columnName));
    34.     }
    35.  
    36.     @Override
    37.     public Degree getResult(ResultSet rs, int columnIndex) throws SQLException {
    38.         return parseDegree(rs.getString(columnIndex));
    39.     }
    40.  
    41.     @Override
    42.     public Degree getResult(CallableStatement cs, int columnIndex) throws SQLException {
    43.         return parseDegree(cs.getString(columnIndex));
    44.     }
    45.  
    46.     private Degree parseDegree(String degree) {
    47.         switch (degree) {
    48.             case "ZK":
    49.                 return Degree.COLLEGE;
    50.             case "BK":
    51.                 return Degree.BACHELOR;
    52.             case "YJS":
    53.                 return Degree.GRADUATE;
    54.             case "BS":
    55.                 return Degree.DOCTORAL;
    56.         }
    57.         return null;
    58.     }
    59. }

    TypeHandler提供了两类方法：setParameter方法用于设置SQL参数，getResult方法用于获取查询的结果

    上述实现中，我们在setParameter方法中将Degree枚举类型的数据转换成数据库表中字段能够识别的数据设置到SQL参数中，可用于查询、新增、修改、查询等操作；在getResult方法中将从数据库表中查询到的字段对应的数据转换成Degree枚举类型的数据；

    修改TeacherMapper.xml配置文件，目的是让查询数据、新增数据时，使用自定义的DegreeTypeHandler

    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.     <resultMap id="teacherInfoMap" type="cn.horse.demo.TeacherInfo">
    8.         <result column="ID" property="id" />
    9.         <result column="TEACHER_NAME" property="name" />
    10.         <result column="DEPARTMENT" property="department" />
    11.         <result column="BIRTH" property="birth" />
    12.         <result column="DEGREE" property="degree" typeHandler="cn.horse.demo.DegreeTypeHandler" />
    13.     resultMap>
    14.  
    15.     <select id="findAll" resultMap="teacherInfoMap">
    16.         SELECT
    17.             ID,
    18.             TEACHER_NAME,
    19.             DEPARTMENT,
    20.             BIRTH,
    21.             DEGREE
    22.         FROM T_TEACHER
    23.     select>
    24.  
    25.     <insert id="insert" parameterType="cn.horse.demo.TeacherInfo">
    26.         INSERT INTO T_TEACHER(ID, TEACHER_NAME, DEPARTMENT, BIRTH, DEGREE)
    27.         VALUES(#{id}, #{name}, #{department}, #{birth}, #{degree,typeHandler=cn.horse.demo.DegreeTypeHandler})
    28.     insert>
    29. mapper>

    查询数据时，在resultMap结果映射的result标签中配置typeHandler属性

    新增数据时，在SQL中使用参数时配置TypeHandler，格式如下：

            #{degree,typeHandler=cn.horse.demo.DegreeTypeHandler}

    1、例子：查询教师列表

    1. // 引入JDK日志配置
    2. System.setProperty("java.util.logging.config.class", "cn.horse.demo.JdkLogConfig");
    3. findAll("cn.horse.demo.TeacherInfoMapper.findAll");

    执行后的结果如下：

    2、例子：新增教师

    1. private static void insert(String statement, TeacherInfo teacherInfo) {
    2.     SqlSession sqlSession = null;
    3.     try {
    4.         sqlSession = SqlSessionUtils.openSession();
    5.         sqlSession.insert(statement, teacherInfo);
    6.     } finally {
    7.         SqlSessionUtils.closeSession(sqlSession);
    8.     }
    9. }

    执行后的结果如下：

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  • 原文地址：https://blog.csdn.net/m1729339749/article/details/132677957