Introduction to XPath in Java programming

1、 Use Dom4j to support XPath operations

- an element can be directly obtained without layer by layer parsing

How to use XPath:

The first form: / AAA / BBB / CCC, one / represents a layer, indicating that the CCC under BBB under AAA is obtained

The second form is / / BBB, which means that the same name can be obtained as long as the name is BBB// DDD / BBB: get all BBBS under all DDDs

The third form: / AAA / BBB / CCC / *, to get all elements under AAA, BBB and CCC/*/*/*/ BBB means to restrict the first three layers. No matter what the name of the first three layers is, you can get all BBBS below them. / / *, Get all the elements.

The fourth form: / AAA / BBB [1], the first BBB under AAA/ AAA / BBB [last()], indicating that the last BBB under AAA is obtained

The fifth form: / / @ ID, which means that you can get / / BBB [@ ID] with ID attribute as long as there is ID attribute on the tag. You can get BBB with ID attribute as long as you have ID attribute on BBB