Spring NamedParameter 异常

Question

我正在尝试使用 spring JdbcTemplate 中的命名参数在 db 中插入值。我正在对 NamedParameter 使用 setter 注入，但它显示了异常。如果我使用构造函数注入，那么它会正常工作。我不知道我在哪里做错了任何人帮助我解决这个问题

代码

Employee.java

public class Employee {
    String name,pwd;
    int en;

    public Employee(String name,String pwd,int en){
        this.en=en;
        this.name=name;
        this.pwd=pwd;
    }

    public String getName(){
        return name;
    }

    public void setName(String name){
        this.name=name;
    }

    public String getPwd(){
        return pwd;
    }
    public void setPwd(String pwd){
        this.pwd=pwd;
    }

    public int getEn(){
        return en;
    }

    public void setEn(int en){
        this.en=en;
    }

}

EmployeeDao.java

import java.sql.*;

import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.PreparedStatementCallback;
import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;

import java.util.*;

import org.springframework.dao.DataAccessException;

public class EmployeeDao {

    NamedParameterJdbcTemplate template;

    public void setTemplate(NamedParameterJdbcTemplate template){
        this.template=template;
    }

    public void save(Employee emp){
        String q="insert into users values(:name,:pwd,:en)";
        Map<String, Object> m=new HashMap<String, Object>();
        m.put("name",emp.getName());
        m.put("pwd",emp.getPwd());
        m.put("en",emp.getEn());

        template.execute(q,m,new PreparedStatementCallback() {  

            public Object doInPreparedStatement(PreparedStatement ps) throws SQLException,DataAccessException{
                return ps.executeUpdate();
            }

        });
    }

}

Test.java

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class Test {

    public static void main(String args[]){
        ApplicationContext ctx=new ClassPathXmlApplicationContext("applicationcontext.xml");

        EmployeeDao emp=(EmployeeDao)ctx.getBean("s");
        emp.save(new Employee("vijay","perfect",123));
    }

}

applicationcontext.xml

<?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:p="http://www.springframework.org/schema/p"  
    xsi:schemaLocation="http://www.springframework.org/schema/beans   
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">  

<bean id="ds" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/LoginTrack"/>
<property name="username" value="root" />
<property name="password" value=""/>
</bean>

<bean id="jtemplate" class="org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate">
<property name="dataSource" ref="ds"/>
</bean>
<bean id="s" class="EmployeeDao">
<property name="template" ref="jtemplate"/>
</bean>
</beans>

堆栈跟踪：

log4j:WARN No appenders could be found for logger (org.springframework.core.env.StandardEnvironment).
log4j:WARN Please initialize the log4j system properly.
Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jtemplate' defined in class path resource [applicationcontext.xml]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate]: No default constructor found; nested exception is java.lang.NoSuchMethodException: org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate.<init>()
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1013)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:959)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:490)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:461)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:626)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:932)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
    at Test.main(Test.java:6)
Caused by: org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate]: No default constructor found; nested exception is java.lang.NoSuchMethodException: org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate.<init>()
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:83)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:1006)
    ... 13 more
Caused by: java.lang.NoSuchMethodException: org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate.<init>()
    at java.lang.Class.getConstructor0(Class.java:2892)
    at java.lang.Class.getDeclaredConstructor(Class.java:2058)
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:78)
    ... 14 more

Answer 1

这是因为您使用默认构造函数为 NamedParameterJdbcTemplate 创建 bean 而它不可用。

修改你的bean定义为：

<bean id="jtemplate" class="org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate">
<constructor-arg ref="ds"/>
</bean>

希望对你有帮助

Answer 2

修改你的xml。改变

<bean id="s" class="EmployeeDao">
    <property name="template" ref="jtemplate"/>
</bean>

到

<bean id="s" class="EmployeeDao">
</bean>

然后在您的 EmployeeDao 类中，将 @Autowired 注释添加到您的 NamedParameterJdbcTemplate 对象

改变

NamedParameterJdbcTemplate template;

到

@Autowired
private NamedParameterJdbcTemplate template;

现在您让 Spring 为您设置它。您也将不再需要 EmployeeDao 类中的 setTemplate(..) 方法