MyBatis 'IN' 子句中的列表 [英] Lists in MyBatis 'IN' clause

问题描述

如何将整数列表传递给 MyBatis XML，以便在 MySQL 查询的 in 子句中使用?

How can I pass an Integer List to MyBatis XML, to be used in an in clause in my MySQL query?

我在 mapper-xml 文件中使用 Java 7、MySQL 5.6 DB 和 MyBatis 3.0.4 进行查询.

I am using Java 7, MySQL 5.6 DB and MyBatis 3.0.4 with queries in a mapper-xml file.

目前，我正在将此整数列表转换为字符串，并使用字符串替换(${} 运算符)将值放入IN"子句中 - 虽然它按预期工作，这种方法使参数容易受到注入攻击.

Presently, I am converting this list of integers to a string, and using string substitution (${} operator) to put the values in the 'IN' clause - while it works as expected, this approach leaves the parameter vulnerable to Injection.

我曾尝试使用 元素，但我不知道要指定哪些属性.

I have tried using a <foreach> element, but I am not able to figure out what attributes to specify.

下面是一个示例 Java 代码:

public List<Stripper> getStripperDetails(String club, List<Integer> stripperIds) {
        Map<String, Object> input = new HashMap<>();
        input.put("club", club);
        input.put("stripperIds", stripperIds);
        return stripClubMapper.getStripperDetails(input);
}

映射器 xml :

<select id="getStripperDetails" parameterType="java.util.HashMap" resultMap="StripperMap">
    SELECT STRIPPER_ID, STAGE_NAME, REAL_NAME, CLUB FROM EXOTIC_DANCERS WHERE CLUB = #{club} AND STRIPPER_ID IN     
    <foreach item="item" index="index" collection="stripperIds" open="(" separator="," close=")">
        #{index}
    </foreach>
</select>

我无法弄清楚要为 <foreach> 元素指定哪些属性 - 对于 #{index} 处的值，我一直遇到 NullPointerException.

I am not able to figure out what attributes to specify for the <foreach> element - I keep running into a NullPointerException for the value at #{index}.

你能帮我理解元素的正确用法吗?

Can you please help me understand the correct usage of the <foreach> element?

@10086 ,

下面是堆栈跟踪:

org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: java.lang.NullPointerException
### The error may involve com.stripclub.mapper.stripClubMapper.getStripperDetails-Inline
### The error occurred while setting parameters
### Cause: java.lang.NullPointerException
    at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:67) ~[mybatis-spring-1.0.0-RC3.jar:1.0.0-RC3]
    at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:345) ~[mybatis-spring-1.0.0-RC3.jar:1.0.0-RC3]
    at com.sun.proxy.$Proxy208.selectList(Unknown Source) ~[na:na]
    at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:193) ~[mybatis-spring-1.0.0-RC3.jar:1.0.0-RC3]
    at org.apache.ibatis.binding.MapperMethod.executeForList(MapperMethod.java:85) ~[mybatis-3.0.4.jar:3.0.4]
    at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:65) ~[mybatis-3.0.4.jar:3.0.4]
    at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:38) ~[mybatis-3.0.4.jar:3.0.4]
    at com.sun.proxy.$Proxy209.getTransactionIds(Unknown Source) ~[na:na]

推荐答案

当与 Lists 一起使用时，应在 foreach 标签内使用 item 属性指定的值.如下使用:

The value specified by the item attribute should be used inside the foreach tag, when used with Lists. Use as below :

    <foreach item="sId" collection="stripperIds" separator="," open="(" close=")">
        #{sId}
    </foreach>

索引属性不是强制性的，当使用列表时.有关更多信息，请参阅 MyBatis 文档部分，或查看 DTD - http://mybatis.org/dtd/mybatis-3-mapper.dtd 有关参数的更多信息:

The index attibute is not mandatory, when using a List. Refer the MyBatis docs section for more info, or check out the DTD - http://mybatis.org/dtd/mybatis-3-mapper.dtd for more info about the parameters :

    <!ELEMENT foreach (#PCDATA | include | trim | where | set | foreach | choose | if | bind)*>
    <!ATTLIST foreach
    collection CDATA #REQUIRED
    item CDATA #IMPLIED
    index CDATA #IMPLIED
    open CDATA #IMPLIED
    close CDATA #IMPLIED
    separator CDATA #IMPLIED
    >

此外，可以在 foreach 中访问对象列表，如下所示.您通常会将其用于 INSERT/UPDATE 语句:

Also, lists of objects can be accessed in foreach as below. You would typically use this for INSERT/UPDATE statements :

示例豆:

public class StripperBean {

    public StripperBean(int stripperID, String stripperName, String realName) {
        this.stripperID = stripperID;
        this.stripperName = stripperName;
        this.realName = realName;
    }

    private int stripperID; 
    private String stripperName;
    private String realName;        

    public int getStripperID() {
        return stripperID;
    }
    public void setStripperID(int stripperID) {
        this.stripperID = stripperID;
    }
    public String getStripperName() {
        return stripperName;
    }
    public void setStripperName(String stripperName) {
        this.stripperName = stripperName;
    }
    public String getRealName() {
        return realName;
    }
    public void setRealName(String realName) {
        this.realName = realName;
    }       
}

在您的实施中:

    Map<String, Object> input = new HashMap<>();
    input.put("club", club);
    List<StripperBean> strippers = new ArrayList<>();
    strippers.add(new StripperBean(1,"Ashley", "Jean Grey"));
    strippers.add(new StripperBean(2,"Candice","Diana Prince"));
    strippers.add(new StripperBean(3,"Cristal","Lara Croft"));        
    input.put("strippers", strippers);
    return stripClubMapper.saveStripperDetails(input);

在映射器 xml 中:

In the mapper xml :

    <insert id="saveStripperDetails">
        INSERT INTO EXOTIC_DANCERS (STRIPPER_ID, STAGE_NAME, REAL_NAME)
        VALUES
        <foreach item="stripper" collection="input" separator=",">
            (#{stripper.stripperID},
            #{stripper.stripperName},
            #{stripper.realName})
        </foreach>
    </select>

好问题顺便说一句:)

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