Unit06： Spring对JDBC的整合支持 Spring+JDBC TemplateSpring异常处理

Posted 2020-09-03 唐胜伟

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Unit06： Spring对JDBC的整合支持、 Spring+JDBC Template 、Spring异常处理

1. springmvc提供的异常处理机制

我们可以将异常抛给spring框架，让spring来帮我们处理异常。

(1)使用简单异常处理器

step1. 配置简单异常处理器。

step2. 添加对应的异常处理页面。
注：该方式只适合处理简单异常的处理，如果要对异常做复杂处理，比如记录日志等，则不合适了。

(2)使用@ExceptionHandler注解

step1. 在处理器类当中，添加一个异常处理方法，该方法要使用@ExceptionHandler注解来标注。

step2.添加对应的异常处理页面。

2. SpringJdbc

(1)SpringJdbc是什么?

是spring框架中的一个模块，对jdbc api做了封装，简化了 jdbc的代码(比如，不用考虑获取连接与关闭连接了)

(2)编程步骤

step1. 导包。

step2. 添加spring配置文件。
step3. 添加JdbcTemplate配置。

注:JdbcTemplate对jdbc的api做了封装。
step4. 调用JdbcTemplate提供的方法。
注：通常将JdbcTemplate注入到DAO。

springmvc提供的异常处理机制代码

src/main/java

controller

package controller;

import javax.servlet.http.HttpServletRequest;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class HelloController {
    @ExceptionHandler
    public String handler(Exception ex,
            HttpServletRequest request){
        System.out.println("handler()");
        /*
         * 依据异常类型，分别进行相应的处理。
         * ex:就是方法所抛出的异常。
         */
        if(ex instanceof NumberFormatException){
            request.setAttribute("msg",
                    "亲，请输入正确的数字");
            return "error";
        }else if(ex instanceof 
                StringIndexOutOfBoundsException){
            request.setAttribute("msg",
                    "下标越界了");
            return "error";
        }else{
            //其它异常
            return "sys_error";
        }
    }
    
    @RequestMapping("/toHello.do")
    public String toHello(){
        System.out.println("toHello()");
        String str = "123a";
        Integer.parseInt(str);
        return "hello";
    }
    
    @RequestMapping("/toHello2.do")
    public String toHello2(){
        System.out.println("toHello2()");
        String str = "abcd";
        str.charAt(10);
        return "hello";
    }
}

HelloController.java

interceptors

package interceptors;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

public class SomeInterceptor implements 
HandlerInterceptor{

    /**
     * 最后执行的方法。
     * ex:处理器所抛出的异常。
     */
    public void afterCompletion(
            HttpServletRequest request, 
            HttpServletResponse response, 
            Object arg2, Exception ex)
            throws Exception {
        System.out.println("afterCompletion()");
    }

    /**
     * 在处理器已经执行完毕，正准备将处理结果
     * (ModelAndView)返回给前端控制器之前，执行
     * postHandle方法。
     * 注：可以在该方法里面，修改处理结果。
     */
    public void postHandle(
            HttpServletRequest request, 
            HttpServletResponse response, 
            Object arg2, ModelAndView mav)
            throws Exception {
        System.out.println("postHandle()");
    }

    /**
     * 如果该方法返回值为true,表示继续向后
     * 调用（即调用后面的拦截器和处理器）；
     * 如果该方法的返回值为false,则不再向后
     * 调用，返回处理结果。
     * arg2: 处理器方法对象。
     */
    public boolean preHandle(
            HttpServletRequest request, 
            HttpServletResponse response,
            Object arg2) throws Exception {
        System.out.println("preHandle()");
        return true;
    }
    
}

SomeInterceptor.java

src/main/resources

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context" 
    xmlns:jdbc="http://www.springframework.org/schema/jdbc"  
    xmlns:jee="http://www.springframework.org/schema/jee" 
    xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:aop="http://www.springframework.org/schema/aop" 
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xmlns:util="http://www.springframework.org/schema/util"
    xmlns:jpa="http://www.springframework.org/schema/data/jpa"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd
        http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.2.xsd
        http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.2.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd
        http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.3.xsd
        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.2.xsd
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd
        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.2.xsd">
    <!-- 配置组件扫描 -->
    <context:component-scan 
    base-package="controller"/>
    <!-- 配置视图解析器 -->
    <bean
     class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <property name="prefix" value="/WEB-INF/"/> 
    <property name="suffix" value=".jsp"/> 
    </bean> 
    
    <!-- 配置拦截器 -->
    <!--  
    <mvc:interceptors>
        <mvc:interceptor>
            <mvc:mapping path="/**"/>
            <bean 
            class="interceptors.SomeInterceptor"/>
        </mvc:interceptor>
    </mvc:interceptors>
    -->
    
    <!-- 配置简单异常处理器 -->
    <!-- 
    <bean 
    class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
        <property name="exceptionMappings">
            <props>
                <prop key="java.lang.NumberFormatException">ex1</prop>
                <prop key="java.lang.StringIndexOutOfBoundsException">ex2</prop>
            </props>
        </property>
    </bean>
     -->
</beans>

spring-mvc.xml

WEB-INF

<%@page pageEncoding="utf-8" 
contentType="text/html; charset=utf-8" %>
<html>
    <head></head>
    <body style="font-size:30px;">
        ${msg}        
    </body>
</html>

error.jsp

<%@page pageEncoding="utf-8" 
contentType="text/html; charset=utf-8" %>
<html>
    <head></head>
    <body style="font-size:30px;">
        请输入正确的数字
    </body>
</html>

ex1.jsp

<%@page pageEncoding="utf-8" 
contentType="text/html; charset=utf-8" %>
<html>
    <head></head>
    <body style="font-size:30px;">
        下标越界
    </body>
</html>

ex2.jsp

<h1>Hello,SpringMVC</h1>

hello.jsp

<%@page pageEncoding="utf-8" 
contentType="text/html; charset=utf-8" %>
<html>
    <head></head>
    <body style="font-size:30px;">
        系统繁忙，稍后重试
    </body>
</html>

sys_error.jsp

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">
  <servlet>
    <servlet-name>action</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <!-- 
         DispatcherServlet的初始化方法在执行时，
         会启动spring容器。
         contextConfigLocation负责指定spring
         配置文件的位置。
     -->
    <init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:spring-mvc.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
    <servlet-name>action</servlet-name>
    <url-pattern>*.do</url-pattern>
</servlet-mapping>
  
</web-app>

web.xml

  <dependencies>
      <dependency>
          <groupId>org.springframework</groupId>
          <artifactId>spring-webmvc</artifactId>
          <version>3.2.8.RELEASE</version>
      </dependency>
  </dependencies>

pom.xml

Spring对JDBC的整合支持、 Spring+JDBC Template

SQL语句：

CREATE table emp_fre(
id number(8) primary key,
name varchar2(50),
age number(3)
);

CREATE sequence emp_seq_fre;

oracle_create_emp.sql

src/main/java

com.tarena.netctoss.controller

package com.tarena.netctoss.controller;

import javax.annotation.Resource;
import javax.servlet.http.HttpServletRequest;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

import com.tarena.netctoss.dao.AdminDAO;
import com.tarena.netctoss.entity.Admin;

@Controller
public class LoginController {
    
    @Resource(name="adminDAO")
    private AdminDAO dao;
    
    @RequestMapping("/toLogin.do")
    public String toLogin(){
        System.out.println("toLogin()");
        return "login";
    }
    
    
    @RequestMapping("/login.do")
    public String login(
            HttpServletRequest request){
        System.out.println("login()");
        String adminCode = 
            request.getParameter("adminCode");
        String pwd = 
            request.getParameter("pwd");
        System.out.println("adminCode:"
            + adminCode + " pwd:" + pwd);
        //使用DAO来访问数据库
        Admin admin = null;
        try{
            admin = 
                dao.findByAdminCode(adminCode);
        }catch(Exception e){
            e.printStackTrace();
            //系统异常，需要提示用户稍后重试
            return "error";
        }
        if(admin == null){
            //帐号错误
            request.setAttribute(
                    "login_failed", "帐号错误");
            return "login";
        }else{
            if(admin.getPassword().equals(pwd)){
                //登录成功
                return "redirect:toIndex.do";
            }else{
                //密码错误
                request.setAttribute(
                        "login_failed", "密码错误");
                return "login";
            }
        }
    }
    
    @RequestMapping("/toIndex.do")
    public String toIndex(){
        return "index";
    }
    
}

LoginController.java

com.tarena.netctoss.dao

package com.tarena.netctoss.dao;

import com.tarena.netctoss.entity.Admin;

public interface AdminDAO {
    public Admin findByAdminCode(String 
            adminCode);
    
}

AdminDAO.java

package com.tarena.netctoss.dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import javax.annotation.Resource;
import javax.sql.DataSource;

import org.springframework.stereotype.Repository;

import com.tarena.netctoss.entity.Admin;

@Repository("adminDAO") 
public class AdminDAOJdbcImpl implements 
    AdminDAO{
    
    @Resource(name="ds")
    private DataSource ds;
    
    public Admin findByAdminCode(
            String adminCode) {
        Admin admin = null;
        Connection conn = null;
        try {
            conn = ds.getConnection();
            String sql = 
                "select * from admin_info_lhh "
                    + "where admin_code=?";
            PreparedStatement ps = 
                    conn.prepareStatement(sql);
            ps.setString(1, adminCode);
            ResultSet rs = 
                    ps.executeQuery();
            if(rs.next()){
                admin = new Admin();
                admin.setAdminId(rs.getInt("admin_id"));
                admin.setAdminCode(rs.getString("admin_code"));
                admin.setPassword(rs.getString("password"));
                admin.setName(rs.getString("name"));
                admin.setTelephone(rs.getString("telephone"));
                admin.setEmail(rs.getString("email"));
                admin.setEnrolldate(rs.getTimestamp("enrolldate"));
            }
        } catch (SQLException e) {
            //记日志
            e.printStackTrace();
            /*
             * 要看异常能否恢复，如果能够恢复，
             * 则立即恢复，如果不能够恢复(
             * 比如，数据库服务停止，一般称这样
             * 的异常为系统异常),则提示用户稍后
             * 重试。
             */
            throw new RuntimeException(e);
        }finally{
            if(conn != null){
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                    throw new RuntimeException(e);
                }
            }
        }
        return admin;
    }

}

AdminDAOJdbcImpl.java

com.tarena.netctoss.entity

package com.tarena.netctoss.entity;

import java.io.Serializable;
import java.sql.Timestamp;

public class Admin implements Serializable {

    private Integer adminId;
    private String adminCode;
    private String password;
    private String name;
    private String telephone;
    private String email;
    private Timestamp enrolldate;
    
    @Override
    public String toString() {
        return "Admin [adminId=" + adminId + ", adminCode=" + adminCode + ", password=" + password + ", name=" + name
                + ", telephone=" + telephone + ", email=" + email + ", enrolldate=" + enrolldate + "]";
    }
    
    public Integer getAdminId() {
        return adminId;
    }
    public void setAdminId(Integer adminId) {
        this.adminId = adminId;
    }
    public String getAdminCode() {
        return adminCode;
    }
    public void setAdminCode(String adminCode) {
        this.adminCode = adminCode;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getTelephone() {
        return telephone;
    }
    public void setTelephone(String telephone) {
        this.telephone = telephone;
    }
    public String getEmail() {
        return email;
    }
    public void setEmail(String email) {
        this.email = email;
    }
    public Timestamp getEnrolldate() {
        return enrolldate;
    }
    public void setEnrolldate(Timestamp enrolldate) {
        this.enrolldate = enrolldate;
    }
    
}

Admin.java

src/main/resources

# db connection parameters
# key=value
driver=oracle.jdbc.driver.OracleDriver
url=jdbc:oracle:thin:@192.168.201.227:1521:orcl
user=openlab
pwd=open123
# datasource parameters
initSize=1
maxSize=1

db.properties

<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xmlns:jdbc="http://www.springframework.org/schema/jdbc" xmlns:jee="http://www.springframework.org/schema/jee" xmlns:tx="http://www.springframework.org/schema/tx" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:util="http://www.springframework.org/schema/util" xmlns:jpa="http://www.springframework.org/schema/data/jpa" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.2.xsd http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.2.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.3.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.2.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.2.xsd">  <context:component-scan base-package="com.tarena.netctoss"/>  <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"<

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