Mybatis plus 存储 List、Map

一、前提概要

1.1 支持环境

数据库支持：MySql版本要求 5.7+

1.2 需求场景

使用MySQL数据库存储时，由于业务要求实体类中特定字段需要使用 自定义类型或者List、Map类型。

二、需求实现

2.1 非自定义数据类型，List、Map

首先：在需要转换的实体类字段上加上：

@TableField(typeHandler = JacksonTypeHandler.class)

接着：在该实体类上修改 @TableName

@TableName(value = "数据库表名",autoResultMap = true)

2.2 自定义类型数据类型

引入依赖：

<properties><jackson-core.version>2.12.6</jackson-core.version><jackson-databind.version>2.12.7.1</jackson-databind.version><jackson-annotations.version>2.15.2</jackson-annotations.version>
</properties><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-core</artifactId><version>${jackson-core.version}</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>${jackson-databind.version}</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-annotations</artifactId><version>${jackson-annotations.version}</version>
</dependency>

首先定义数据处理工具类：

@Component
public class ObjectToJackson {private static ObjectMapper mapper;@Resourcepublic void setMapper(ObjectMapper mapper) {ObjectToJackson.mapper = mapper;}public static <T> String objectToJson(T o) {try {return ObjectToJackson.mapper.writeValueAsString(o);} catch (Exception e) {e.printStackTrace();throw new ServerException(500);}}public static <T> T jsonToObject(String s, TypeReference<T> typeReference) {if (s == null) {return null;}try {return ObjectToJackson.mapper.readValue(s, typeReference);} catch (JsonProcessingException e) {e.printStackTrace();throw new ServerException(500);}}
}

接着定义自己的转化规则：

public class ObjectToJacksonHandler extends BaseTypeHandler<Object> {@Overridepublic void setNonNullParameter(PreparedStatement ps, int i, Object parameter, JdbcType jdbcType) throws SQLException {String json = ObjectToJackson.objectToJson(parameter);ps.setString(i, json);}@Overridepublic Object getNullableResult(ResultSet rs, String columnName) throws SQLException {String string = rs.getString(columnName);return ObjectToJackson.jsonToObject(string, new TypeReference<>() {});}@Overridepublic Object getNullableResult(ResultSet rs, int columnIndex) throws SQLException {String string = rs.getString(columnIndex);return ObjectToJackson.jsonToObject(string, new TypeReference<>() {});}@Overridepublic Object getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {String string = cs.getString(columnIndex);return ObjectToJackson.jsonToObject(string, new TypeReference<>() {});}
}

使用：

@TableName(value = "数据库表名", autoResultMap = true)@TableField(typeHandler = ObjectToJacksonHandler.class)