org.apache.ibatis.ognl.OgnlException:怎么解决

Question

Caused by: org.apache.ibatis.ognl.OgnlException: source is null for getProperty(null, "mainPic")
at org.apache.ibatis.ognl.OgnlRuntime.getProperty(OgnlRuntime.java:1652) ~[mybatis-3.2.2-3.2.2.jar:3.2.2]
at org.apache.ibatis.ognl.ASTProperty.getValueBody(ASTProperty.java:92) ~[mybatis-3.2.2-3.2.2.jar:3.2.2]
at org.apache.ibatis.ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:170) ~[mybatis-3.2.2-3.2.2.jar:3.2.2]
at org.apache.ibatis.ognl.SimpleNode.getValue(SimpleNode.java:210) ~[mybatis-3.2.2-3.2.2.jar:3.2.2]
at org.apache.ibatis.ognl.ASTChain.getValueBody(ASTChain.java:109) ~[mybatis-3.2.2-3.2.2.jar:3.2.2]
at org.apache.ibatis.ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:170) ~[mybatis-3.2.2-3.2.2.jar:3.2.2]
at org.apache.ibatis.ognl.SimpleNode.getValue(SimpleNode.java:210) ~[mybatis-3.2.2-3.2.2.jar:3.2.2]
at org.apache.ibatis.ognl.ASTNotEq.getValueBody(ASTNotEq.java:49) ~[mybatis-3.2.2-3.2.2.jar:3.2.2]
at org.apache.ibatis.ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:170) ~[mybatis-3.2.2-3.2.2.jar:3.2.2]
at org.apache.ibatis.ognl.SimpleNode.getValue(SimpleNode.java:210) ~[mybatis-3.2.2-3.2.2.jar:3.2.2]
at org.apache.ibatis.ognl.ASTAnd.getValueBody(ASTAnd.java:56) ~[mybatis-3.2.2-3.2.2.jar:3.2.2]
at org.apache.ibatis.ognl.SimpleNode.evaluateGetValueBody(SimpleNode.java:170) ~[mybatis-3.2.2-3.2.2.jar:3.2.2]
at org.apache.ibatis.ognl.SimpleNode.getValue(SimpleNode.java:210) ~[mybatis-3.2.2-3.2.2.jar:3.2.2]
at org.apache.ibatis.ognl.Ognl.getValue(Ognl.java:333) ~[mybatis-3.2.2-3.2.2.jar:3.2.2]
at org.apache.ibatis.ognl.Ognl.getValue(Ognl.java:413) ~[mybatis-3.2.2-3.2.2.jar:3.2.2]
at org.apache.ibatis.ognl.Ognl.getValue(Ognl.java:395) ~[mybatis-3.2.2-3.2.2.jar:3.2.2]
at org.apache.ibatis.scripting.xmltags.OgnlCache.getValue(OgnlCache.java:45) ~[mybatis-3.2.2-3.2.2.jar:3.2.2]
... 106 common frames omitted