Why the Unmarshaller is not generating error on invalid data given in the XML file?

In the Reference Implementation and JRE 8 implementation of JAXB, the Unmarshaller does not have any default data validation. If the input XML has any invalid data, the Unmarshaller will will throw data parsing exceptions or assign null values.

1. Null value example - Create the following invalid XML file, UserError1.xml:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<User ID="2">
    <BirthDate>Unknown</BirthDate>
    <Name>Frank Y. Ivy</Name>
    <Sex>Male</Sex>
</User>

Run the MyXmlToUser.java program given in the previous tutorial. The Unmarshaller returns null for the invalid date in the XML:

fyicenter> java -cp .:../jaxb-ri/mod/jaxb-api.jar:\
  ../jaxb-ri/mod/jaxb-runtime.jar:\
  ../jaxb-ri/mod/istack-commons-runtime.jar:\
  ../jaxb-ri/mod/javax.activation-api.jar \
  MyXmlToUser.java UserError1.xml
Unmarshal XML file to user object...
My user object:
   Name: Frank Y. Ivy
   BirthDate: null
   Sex: Male
   ID: 2

fyicenter> \local\jdk-1.8.0\bin\java MyXmlToUser UserError1.xml
Unmarshal XML file to user object...
My user object:
   Name: Frank Y. Ivy
   BirthDate: null
   Sex: Male
   ID: 2

2. Data parsing exception example - Create the following invalid XML file, UserError2.xml:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<User ID="two">
    <BirthDate>Unknown</BirthDate>
    <Name>Frank Y. Ivy</Name>
    <Sex>Male</Sex>
</User>

Run the MyXmlToUser.java program given in the previous tutorial. The Unmarshaller returns NumberFormatException for the invalid integer in the XML:

fyicenter> java -cp .:../jaxb-ri/mod/jaxb-api.jar:\
  ../jaxb-ri/mod/jaxb-runtime.jar:\
  ../jaxb-ri/mod/istack-commons-runtime.jar:\
  ../jaxb-ri/mod/javax.activation-api.jar \
  MyXmlToUser.java UserError2.xml
Exception in thread "main" java.lang.NumberFormatException: Not a number: two
  at com.sun.xml.bind.DatatypeConverterImpl._parseInt(DatatypeConverterImpl.java:125)
  at com.sun.xml.bind.v2.model.impl.RuntimeBuiltinLeafInfoImpl$18.parse(RuntimeBuiltinLeafInfoImpl.java:742)
  at com.sun.xml.bind.v2.model.impl.RuntimeBuiltinLeafInfoImpl$18.parse(RuntimeBuiltinLeafInfoImpl.java:740)
  ...

fyicenter> \local\jdk-1.8.0\bin\javac MyXmlToUser.java
fyicenter> \local\jdk-1.8.0\bin\java MyXmlToUser UserError2.xml
Exception in thread "main" java.lang.NumberFormatException: Not a number: two
   at com.sun.xml.internal.bind.DatatypeConverterImpl._parseInt(DatatypeConverterImpl.java:110)
   at com.fyicenter.demo.User_JaxbXducedAccessor_id.parse(TransducedAccessor_field_Integer.java:57)
   at com.sun.xml.internal.bind.v2.runtime.unmarshaller.StructureLoader.startElement(StructureLoader.java:195)
...

⇒ MyXmlValidator.java - Unmarshal XML File with Schema Validation

⇐ MyXmlToUser.java - Unmarshal XML File to Data Object to

⇑ Examples for JAXB (Java Architecture for XML Binding)

⇑⇑ FAQ for jaxb-*.jar - Java Architecture for XML Binding