ssm框架下实体类属性报空指针

Question

org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.builder.BuilderException: **Error evaluating expression 'user.id!=''||user.id!=null'.** Cause: org.apache.ibatis.ognl.OgnlException: source is null for getProperty(null, "id")
    at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:75)
    at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:371)

Answer 1

    <if test="usr!=null">
        <if test="usr.id!=null"> and u_id=#{usr.id} </if>
    </if>