java filter 返回错误消息_利用java filter 实现业务异常拦截 跳转到错误信息提示页面...
1、緣由：我們在做項目中肯定都會遇到自定義業(yè)務(wù)異常 ，然后將業(yè)務(wù)異常信息跳轉(zhuǎn)的統(tǒng)一的信息提示頁面的情況，比如我們在struts的時候我們會用到struts的異常處理機(jī)制，我們在業(yè)務(wù)層會跑出我們遇到業(yè)務(wù)處理異常 ，然后交由struts處理將提示信息到一個頁面進(jìn)行顯示，來提示用戶的相關(guān)操作，這里我們會根據(jù)以上情景設(shè)計一下怎么來顯示該功能。
2、解決方法：我們的業(yè)務(wù)異常通常都是拋出的，就是unchecked exception，所以最后總會到達(dá)調(diào)用該方法的最外層進(jìn)行捕獲，一般我們都會在action中調(diào)用我們的業(yè)務(wù)方法 ，而業(yè)務(wù)方法可能會跑出異常，此時我們就可以在此時做些文章了， 我們可以利用filter，來捕獲我們拋出的異常，然后跳轉(zhuǎn)到一個統(tǒng)一頁面，進(jìn)行信息提示了。
3、具體代碼：
①自定義異常類，我想這個就不用多說了 ，大家都是會的：
BsException.java
package com.ajun.exception;
/**
* 業(yè)務(wù)異常類
* @author ajun
* @http://blog.csdn.net/ajun_studio
*/
public class BsException extends RuntimeException {
//異常代碼
private String key;
private Object[] values;//一些其他信息
public BsException() {
super();
}
public BsException(String message, Throwable throwable) {
super(message, throwable);
}
public BsException(String message) {
super(message);
}
public BsException(Throwable throwable) {
super(throwable);
}
public BsException(String message,String key){
super(message);
this.key = key;
}
public BsException(String message,String key,Object value){
super(message);
this.key = key;
this.values = new Object[]{value};
}
public BsException(String message,String key,Object[] values){
super(message);
this.key = key;
this.values = values;
}
public String getKey() {
return key;
}
public Object[] getValues() {
return values;
}
}
package com.ajun.exception;
/**
* 業(yè)務(wù)異常類
* @author ajun
* @http://blog.csdn.net/ajun_studio
*/
public class BsException extends RuntimeException {
//異常代碼
private String key;
private Object[] values;//一些其他信息
public BsException() {
super();
}
public BsException(String message, Throwable throwable) {
super(message, throwable);
}
public BsException(String message) {
super(message);
}
public BsException(Throwable throwable) {
super(throwable);
}
public BsException(String message,String key){
super(message);
this.key = key;
}
public BsException(String message,String key,Object value){
super(message);
this.key = key;
this.values = new Object[]{value};
}
public BsException(String message,String key,Object[] values){
super(message);
this.key = key;
this.values = values;
}
public String getKey() {
return key;
}
public Object[] getValues() {
return values;
}
}
既然要用到filter ，自然少不了實現(xiàn)Filter接口，攔截你想要的請求，然后，就可以捕獲異常了，此時你可以對你的chain.doFilter進(jìn)行try catch，然后判斷你想捕獲的異常，很簡單 ，請看代碼：
package com.ajun.filter;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.ajun.exception.BsException;
/**
* 業(yè)務(wù)異常過濾器
* @author ajun
* @http://blog.csdn.net/ajun_studio
*/
public class ExceptionFiler implements Filter {
private String errorPage;//跳轉(zhuǎn)的錯誤信息頁面
public void destroy() {
}
public void doFilter(ServletRequest req, ServletResponse res,
FilterChain chain) throws IOException, ServletException {
HttpServletResponse response = (HttpServletResponse) res;
HttpServletRequest request = (HttpServletRequest) req;
//捕獲你拋出的業(yè)務(wù)異常
try {
chain.doFilter(req, res);
} catch (RuntimeException e) {
if(e instanceof BsException){//如果是你定義的業(yè)務(wù)異常
request.setAttribute("BsException", e);//存儲業(yè)務(wù)異常信息類
request.getRequestDispatcher(errorPage).forward(request, response);//跳轉(zhuǎn)到信息提示頁面！！
}
e.printStackTrace();
}
}
//初始化讀取你配置的提示頁面路徑
public void init(FilterConfig config) throws ServletException {
//讀取錯誤信息提示頁面路徑
errorPage = config.getInitParameter("errorPage");
if(null==errorPage || "".equals(errorPage)){
throw new RuntimeException("沒有配置錯誤信息跳轉(zhuǎn)頁面,請再web.xml中進(jìn)行配置\n\nerrorPage\n/error.jsp\n \n路徑可以是你自己設(shè)定的任何有效路徑頁面！！");
//System.out.println("沒有配置錯誤信息跳轉(zhuǎn)頁面");
}
}
}
package com.ajun.filter;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.ajun.exception.BsException;
/**
* 業(yè)務(wù)異常過濾器
* @author ajun
* @http://blog.csdn.net/ajun_studio
*/
public class ExceptionFiler implements Filter {
private String errorPage;//跳轉(zhuǎn)的錯誤信息頁面
public void destroy() {
}
public void doFilter(ServletRequest req, ServletResponse res,
FilterChain chain) throws IOException, ServletException {
HttpServletResponse response = (HttpServletResponse) res;
HttpServletRequest request = (HttpServletRequest) req;
//捕獲你拋出的業(yè)務(wù)異常
try {
chain.doFilter(req, res);
} catch (RuntimeException e) {
if(e instanceof BsException){//如果是你定義的業(yè)務(wù)異常
request.setAttribute("BsException", e);//存儲業(yè)務(wù)異常信息類
request.getRequestDispatcher(errorPage).forward(request, response);//跳轉(zhuǎn)到信息提示頁面！！
}
e.printStackTrace();
}
}
//初始化讀取你配置的提示頁面路徑
public void init(FilterConfig config) throws ServletException {
//讀取錯誤信息提示頁面路徑
errorPage = config.getInitParameter("errorPage");
if(null==errorPage || "".equals(errorPage)){
throw new RuntimeException("沒有配置錯誤信息跳轉(zhuǎn)頁面,請再web.xml中進(jìn)行配置\n\nerrorPage\n/error.jsp\n \n路徑可以是你自己設(shè)定的任何有效路徑頁面！！");
//System.out.println("沒有配置錯誤信息跳轉(zhuǎn)頁面");
}
}
}
Filter在web.xml中的配置如下：
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ExceptionFilter
com.ajun.filter.ExceptionFiler
errorPage
/error.jsp
ExceptionFilter
*.do
ExceptionFilter
com.ajun.filter.ExceptionFiler
errorPage
/error.jsp
ExceptionFilter
*.do
下面寫個servlet ，在請求的時候拋出你定義業(yè)務(wù)異常來試驗一下吧
package com.ajun.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ExServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
TestService t = new TestService();
t.add();//模擬調(diào)用業(yè)務(wù)層方法，在此方法內(nèi)拋出異常，此異常會在filter中進(jìn)行捕獲。
}
}
package com.ajun.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ExServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
TestService t = new TestService();
t.add();//模擬調(diào)用業(yè)務(wù)層方法，在此方法內(nèi)拋出異常，此異常會在filter中進(jìn)行捕獲。
}
}
web.xml配置上述servlet
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ExServlet
com.ajun.servlet.ExServlet
ExServlet
*.do
ExServlet
com.ajun.servlet.ExServlet
ExServlet
*.do
測試時在servlet中被調(diào)用的業(yè)務(wù)類
TestService.java
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package com.ajun.servlet;
import com.ajun.exception.BsException;
public class TestService {
public void add(){
System.out.println("add () was called!!");
if(true){
throw new BsException("in add() throws exception!!");//拋出異常，根據(jù)你的業(yè)務(wù)邏輯
}
}
}
package com.ajun.servlet;
import com.ajun.exception.BsException;
public class TestService {
public void add(){
System.out.println("add () was called!!");
if(true){
throw new BsException("in add() throws exception!!");//拋出異常，根據(jù)你的業(yè)務(wù)邏輯
}
}
}
成功跳轉(zhuǎn)到error.jsp:顯示：in add() throws exception!!
在后臺得到：
com.ajun.exception.BsException: in add() throws exception!!
at com.ajun.servlet.TestService.add(TestService.java:11)
at com.ajun.servlet.ExServlet.doPost(ExServlet.java:26)
at com.ajun.servlet.ExServlet.doGet(ExServlet
總結(jié)
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