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mybatis返回map数据空值字段不显示

查询sql添加每个字段的判断空

IFNULL(rate,'') as rate

ResultType利用实体返回

不用map

springMVC+mybatis查询数据

返回resultType=”map”时，如果数据为空的字段，则该字段省略不显示，可以通过添加配置文件，规定查询数据为空是则返回null。

<xml version="1.0" encoding="UTF-8">
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD SQL MAP Config 3.1//EN"
  "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
 <settings>
  <setting name="callSettersOnNulls" value="true"/>
 </settings>
</configuration>

spring-mybatis.xml

<!-- spring和MyBatis完美整合，添加mybatis的配置映射文件 -->
 <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
  <property name="dataSource" ref="dataSource"/>
  <property name="configLocation" value="classpath:mybatis-configuration.xml"/>
  <!-- 自动扫描mapping.xml文件 -->
  <property name="mapperLocations" value="classpath:mapping/*.xml"></property>
 </bean>

如果想要配置rate的默认值，例如“”字符串，则可以建立一个类，实现Mybatis的TypeHandler接口

public class EmptyStringIfNull implements TypeHandler<String> {
  @Override
  public String getResult(ResultSet rs, String columnName) throws SQLException {
  return (rs.getString(columnName) == null)  "" : rs.getString(columnName);
  }
  @Override
  public String getResult(ResultSet rs, int columnIndex) throws SQLException {
  return (rs.getString(columnIndex) == null)  "" : rs.getString(columnIndex);
  }
  @Override
  public String getResult(CallableStatement cs, int columnIndex)  throws SQLException {
  return (cs.getString(columnIndex) == null)  "" : cs.getString(columnIndex);
  }
  @Override
  public void setParameter(PreparedStatement ps, int arg1, String str, JdbcType jdbcType) throws SQLException { }}

在sql.xml文件定义与使用如下如下

<resultMap id="find" type="java.util.LinkedHashMap">
  <result property="name" column="name" />
  <result property="phone" column="phone" />
  <result property="rate" column="rate" typeHandler="com.mybatis.EmptyStringIfNull"/>
</resultMap>

mybatis返回map空值未返回字段

mybatis 开启CallSettersOnNulls

@Bean
public SqlSessionFactory sqlSessionFactoryBean() throws Exception
{
  SqlSessionFactoryBean sqlSessionFactoryBean = new   SqlSessionFactoryBean();
  sqlSessionFactoryBean.setDataSource(dataSource());
  Configuration configuration = new .Configuration();
  configuration.setCallSettersOnNulls(true);//map返回空字段消失问题
  PageInterceptor pagePlugin = new PageInterceptor();
  JalorResultSetInterceptor jalorResultSetPlugin = new JalorResultSetInterceptor();
  ProgramInterceptor programPlugin = new ProgramInterceptor();
  //添加插件
  sqlSessionFactoryBean.setPlugins(new Interceptor[] {pagePlugin, jalorResultSetPlugin, programPlugin});
  sqlSessionFactoryBean.setConfiguration(configuration);
  return sqlSessionFactoryBean.getObject();
}

以上为个人经验，希望能给大家一个参考，也希望大家多多支持源码搜藏网。