mybatis返回map型別資料空值欄位不顯示(三種解決方法)
阿新 • • 發佈:2019-02-02
一、查詢sql新增每個欄位的判斷空
IFNULL(rate,'') as rate
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二、ResultType利用實體返回,不用map
三、springMVC+mybatis查詢資料,返回resultType=”map”時,如果資料為空的欄位,則該欄位省略不顯示,可以通過新增配置檔案,規定查詢資料為空是則返回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>
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spring-mybatis.xml
<!-- spring和MyBatis完美整合,新增mybatis的配置對映檔案 -->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean" >
<property name="dataSource" ref="dataSource"/>
<property name="configLocation" value="classpath:mybatis-configuration.xml"/>
<!-- 自動掃描mapping.xml檔案 -->
<property name="mapperLocations" value="classpath:mapping/*.xml"></property>
</bean>
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如果想要配置rate的預設值,例如“”字串,則可以建立一個類,實現Mybatis的TypeHandler介面
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 { }}
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在sql.xml檔案定義與使用如下如下
<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>