when null is passed in the front end, we are very confused when it is clearly null,. Why is the if condition judgment invalid in the xml file of mybatis?
< if test= "name! = null and name! =""" >
identity_id = -sharp{idcard,javaType=String,jdbcType=VARCHAR} < / if >
or spliced sql,
other projects have been judged in this way all the time, but now there is a problem with the new project
problem is the string representation of the Object parameter returned by public static String valueOf (Object obj)
.
parameter:
obj-an Object.
returns:
if the parameter is null, the string is equal to "null"; otherwise, the value of obj.toString () is returned
String name = null;
Object value = null;
System.err.println(name == String.valueOf(value)); //false
System.err.println(name == value); //true
//System.err.println(name.equals(value)); //
//System.err.println(name.equals( String.valueOf(value))); //
System.err.println("null".equals( String.valueOf(value))); //true
System.err.println("null".equals(value)); //false
System.err.println(name == (String)value); //true
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