Detailed explanation of Java Servlet coding and exception handling

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1. Servlet outputs Chinese

(1) Why are there garbled characters? ?

When the out.println method is output or when the form is submitted, the browser will encode the Chinese parameter values ​​​​in the form;

Note: The form will be used The encoding method used when opening the page is encoded. The server side will use ISO-8859-1 for decoding by default, so garbled characters will be generated

(2) How to solve it?

1)Post request: requset.setcharcterencoding(string charset); added before all get parameters and this method only supports post method

2)Get request: modify server settings

2. Read the request parameter value

(1)String request.getParameter(String paramName)

a. If the request parameter name is written incorrectly, a null value will be obtained.

b. For the form (text input box), if you fill in nothing, you will get "".

(2)String[] request.getParameterValues(String paramName)

a. When there are multiple request parameter names with the same name, it should Use this method.

b. For multi-select boxes, if none is selected, a null value will be obtained.

Set the output encoding method arg1.setContentType("text/html;charset=utf-8");

Function

1)Set return The data (mime) type given to the browser; tell the server the data type and encoding returned

2) Set what character set encoding to use when outputting the out.print method

Exception handling: step1. Note Log (keep on-site)

step2. Check whether the exception can be recovered immediately. If it cannot be recovered (for example, the database service stops, the network is interrupted, we can call such an exception a system exception), prompt the user to try again later. Try it (we will use an operation and maintenance sacrifice), and if it can be restored, restore it immediately.

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