Question

//Located in com\src\myproject\services

package com.src.myproject.services;

public interface IMyService {
    public boolean Method1();

}

//Located in com\src\myproject\services

package com.src.myproject.services;

public class MyService implements IMyService {


    @Autowired
    private TestMapper testMapper;

    @Override
    public boolean Method1() {


        return gettestMapper().GetOrder(1); //Get null pointer exception as testMapper is null in debug mode
    }



    public TestMapper gettestMapper(){

            return testMapper;
        }


    public void settestMapper(TestMapper testMapper){
        this.testMapper=testMapper;
        }

}

My mapper.java files are located under com\src\mappers

and corresponding mapper.xml is located under src\main\resources\com\src\myproject\mappers

My servelet-context.xml file is

<?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"
xmlns:tx="http://www.springframework.org/schema/tx" xmlns:context="http://www.springframework.org/schema/context"
xmlns:util="http://www.springframework.org/schema/util"
xsi:schemaLocation="http://www.springframework.org/schema/beans 
                    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd 
                    http://www.springframework.org/schema/tx 
                    http://www.springframework.org/schema/tx/spring-tx-3.0.xsd 
                    http://www.springframework.org/schema/context 
                    http://www.springframework.org/schema/context/spring-context-3.0.xsd
                    http://www.springframework.org/schema/util
                    http://www.springframework.org/schema/util/spring-util-3.1.xsd">


    <!-- Root Context: defines shared resources visible to all other web components -->

    <context:property-placeholder location="/WEB-INF/spring/jdbc.properties,/WEB-INF/spring/mybatis.properties" />

    <context:component-scan base-package="com.src.myproject.controllers" />
    <context:component-scan base-package="com.src.myproject.services" />


    <!-- Enable annotation style of managing transactions -->
    <tx:annotation-driven transaction-manager="transactionManager" />

    <!-- Declare a datasource that has pooling capabilities -->
    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
    destroy-method="close" p:driverClass="${app.jdbc.driverClassName}"
    p:jdbcUrl="${app.jdbc.url}" p:user="${app.jdbc.username}" p:password="${app.jdbc.password}"
    p:acquireIncrement="10" p:idleConnectionTestPeriod="60" p:maxPoolSize="100"
    p:maxStatements="50" p:minPoolSize="10" />

    <!-- Declare a transaction manager -->
    <bean id="transactionManager"
    class="org.springframework.jdbc.datasource.DataSourceTransactionManager"
    p:dataSource-ref="dataSource"
    autowire="byName" />


    <!-- define the SqlSessionFactory, notice that configLocation is not needed when you use MapperFactoryBean -->
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource" />
        <property name="typeAliasesPackage" value="${typeAliasesPackage}" />
    </bean>

    <!-- scan for mappers and let them be autowired -->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="com.src.myproject.mappers" />
         <property name="sqlSessionFactory" ref="sqlSessionFactory" />
    </bean> 
</beans>

The autowiring in the services files is always null and gives null ref exception when I try to use any method from the mapper files via auto wire.

Answer 1

You should never instantiate Spring beans directly. It’s the container that is responsible for object creation. Thus in your controller, instead of:

IMyService mySvc = new Service();

Create such field:

@Autowired
private IMyService mySvc;

Spring will discover it and assign proper value, which is an instance of MyService creates beforehand for you.