Java action类调用DAO的服务方法时出现空指针异常

当我从action调用DAO的方法时，我得到一个空指针异常。我不知道，为什么我会得到它。当我检查代码时，它似乎是正确的 行动课

public String getReport() {
    System.out.println("Inside Action");
    ExpenseReportBean bean=new ExpenseReportBean();
    try {
        getexpenseReport=reportdao.getReport();
        return "success";
    } catch (Exception e) {
        e.printStackTrace();
        return "success";

    }
}

DAO类：

public List<ExpenseReportBean> getReport() {
    System.out.println("Inside DAO");
    sqlQ = "select expense_date,SUM(IF(expense_name='salary',amount,0)) as salary,\n"
                + "SUM(IF(expense_name='rent',amount,0)) as rent\n"
                + "from am_expense\n"
                + "group by DATE_FORMAT(expense_date,'%d-%m-%Y')";

    System.out.println("Inside DAO : SQL =" + sqlQ);
    return jdbcTemplate.query(sqlQ, new RowMapper() {
        public ExpenseReportBean mapRow(ResultSet rs, int i) throws SQLException {
            ExpenseReportBean bean = new ExpenseReportBean();
            bean.setSalary(rs.getString("salary"));
            bean.setRent(rs.getString("rent"));
            bean.setExpense_date(rs.getString("expense_date"));
            System.out.println("Bean= "+rs.getString("rent"));
            return bean;
        }
    });

}

---

你可以检查reportdao对象和它的bean配置之间的连接吗。我猜这个对象是空的。我检查它。这是bean配置：它不是通过使用reportdao instancehi Sathish的getter/setter方法自动创建对象。你能粘贴你的整个动作类吗？你在哪里使用bean引用ExpenseReportBean=newExpenseReportBean（）；？您已经创建了一个对象，需要在该对象上像bean.getReport（）一样调用r8；你可以检查reportdao对象和它的bean配置之间的连接吗。我猜这个对象是空的。我检查它。这是bean配置：它不是通过使用reportdao instancehi Sathish的getter/setter方法自动创建对象。你能粘贴你的整个动作类吗？你在哪里使用bean引用ExpenseReportBean=newExpenseReportBean（）；？您已经创建了一个对象，需要在该对象上像bean.getReport（）一样调用r8；

<action name="getReportAction" class="com.ams.actions.ExpenseReportAction" method="getReport">
            <result name="success" type="json">
                <param name="root">getexpenseReport</param>
            </result>
        </action>

 <bean id="expenseReportdao" class="com.ams.dao.ExpenseReportDao">
        <property name="jdbcTemplate" ref="jdbcTemplate"></property>
    </bean>

Execute
Info:   Inside Action
Severe:   java.lang.NullPointerException
    at com.ams.actions.ExpenseReportAction.getReport(ExpenseReportAction.java:27)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)